diff --git a/.php_cs.dist b/.php_cs.dist
index 984060b3bc..6e4d4c3cd4 100644
--- a/.php_cs.dist
+++ b/.php_cs.dist
@@ -7,19 +7,25 @@ $finder = PhpCsFixer\Finder::create()
 return PhpCsFixer\Config::create()
     ->setFinder($finder)
     ->setRules([
+        '@PHP71Migration' => true,
+        '@PhpCsFixer' => true,
+        '@PHPUnit60Migration:risky' => true,
         '@PSR2' => true,
         '@Symfony' => true,
-        'single_blank_line_before_namespace' => false,
-        'ordered_imports' => true,
         'array_syntax' => ['syntax' => 'short'],
-        'phpdoc_order' => true,
-        'ternary_to_null_coalescing' => true,
-        'no_useless_else' => true,
-        '@PHPUnit60Migration:risky' => true,
-        'php_unit_dedicate_assert' => ['target' => 'newest'],
+        'is_null' => true,
+        'method_argument_space' => ['on_multiline' => 'ensure_fully_multiline'],
         'native_function_invocation' => true,
         'no_alias_functions' => true,
+        'no_useless_else' => true,
         'nullable_type_declaration_for_default_null_value' => true,
+        'ordered_imports' => true,
+        'php_unit_dedicate_assert' => ['target' => 'newest'],
+        'php_unit_test_class_requires_covers' => false,
+        'phpdoc_order' => true,
+        'phpdoc_types_order' => ['null_adjustment' => 'always_last'],
+        'ternary_to_null_coalescing' => true,
         'visibility_required' => ['property', 'method', 'const'],
+        'void_return' => true,
     ])
 ;
diff --git a/src/AbstractUpdateAction.php b/src/AbstractUpdateAction.php
index 0b3f83d217..ebf3ccae83 100644
--- a/src/AbstractUpdateAction.php
+++ b/src/AbstractUpdateAction.php
@@ -81,7 +81,7 @@ public function setVersion($version)
     /**
      * Returns document version.
      *
-     * @return string|int Document version
+     * @return int|string Document version
      */
     public function getVersion()
     {
@@ -112,7 +112,7 @@ public function setVersionType($versionType)
     /**
      * Returns document version type.
      *
-     * @return string|int Document version type
+     * @return int|string Document version type
      */
     public function getVersionType()
     {
@@ -356,7 +356,7 @@ public function hasReplication()
     }
 
     /**
-     * @param Document|array $data
+     * @param array|Document $data
      *
      * @return $this
      */
diff --git a/src/Aggregation/AbstractSimpleAggregation.php b/src/Aggregation/AbstractSimpleAggregation.php
index b9538c829f..ad836c3ef9 100644
--- a/src/Aggregation/AbstractSimpleAggregation.php
+++ b/src/Aggregation/AbstractSimpleAggregation.php
@@ -21,7 +21,7 @@ public function setField(string $field): self
     /**
      * Set a script for this aggregation.
      *
-     * @param string|\Elastica\Script\AbstractScript $script
+     * @param \Elastica\Script\AbstractScript|string $script
      *
      * @return $this
      */
diff --git a/src/Aggregation/BucketScript.php b/src/Aggregation/BucketScript.php
index 568809d0c4..bfdbe0d4b7 100644
--- a/src/Aggregation/BucketScript.php
+++ b/src/Aggregation/BucketScript.php
@@ -71,7 +71,8 @@ public function toArray(): array
     {
         if (!$this->hasParam('buckets_path')) {
             throw new InvalidException('Buckets path is required');
-        } elseif (!$this->hasParam('script')) {
+        }
+        if (!$this->hasParam('script')) {
             throw new InvalidException('Script parameter is required');
         }
 
diff --git a/src/Aggregation/GeoDistance.php b/src/Aggregation/GeoDistance.php
index f80810e10d..3905f87993 100644
--- a/src/Aggregation/GeoDistance.php
+++ b/src/Aggregation/GeoDistance.php
@@ -20,7 +20,7 @@ class GeoDistance extends AbstractAggregation
     /**
      * @param string       $name   the name if this aggregation
      * @param string       $field  the field on which to perform this aggregation
-     * @param string|array $origin the point from which distances will be calculated
+     * @param array|string $origin the point from which distances will be calculated
      */
     public function __construct(string $name, string $field, $origin)
     {
@@ -43,7 +43,7 @@ public function setField(string $field): self
     /**
      * Set the origin point from which distances will be calculated.
      *
-     * @param string|array $origin valid formats are array("lat" => 52.3760, "lon" => 4.894), "52.3760, 4.894", and array(4.894, 52.3760)
+     * @param array|string $origin valid formats are array("lat" => 52.3760, "lon" => 4.894), "52.3760, 4.894", and array(4.894, 52.3760)
      *
      * @return $this
      */
diff --git a/src/Aggregation/ParentAggregation.php b/src/Aggregation/ParentAggregation.php
index 6f2704b392..daef41c98f 100644
--- a/src/Aggregation/ParentAggregation.php
+++ b/src/Aggregation/ParentAggregation.php
@@ -9,11 +9,6 @@
  */
 class ParentAggregation extends AbstractAggregation
 {
-    protected function _getBaseName()
-    {
-        return 'parent';
-    }
-
     /**
      * Set the child type for this aggregation.
      *
@@ -25,4 +20,9 @@ public function setType($type): self
     {
         return $this->setParam('type', $type);
     }
+
+    protected function _getBaseName()
+    {
+        return 'parent';
+    }
 }
diff --git a/src/Aggregation/Range.php b/src/Aggregation/Range.php
index d66551e5b2..7d0272b40d 100644
--- a/src/Aggregation/Range.php
+++ b/src/Aggregation/Range.php
@@ -14,8 +14,8 @@ class Range extends AbstractSimpleAggregation
     /**
      * Add a range to this aggregation.
      *
-     * @param int|float $fromValue low end of this range, exclusive (greater than or equal to)
-     * @param int|float $toValue   high end of this range, exclusive (less than)
+     * @param float|int $fromValue low end of this range, exclusive (greater than or equal to)
+     * @param float|int $toValue   high end of this range, exclusive (less than)
      * @param string    $key       customized key value
      *
      * @throws \Elastica\Exception\InvalidException
diff --git a/src/Aggregation/TopHits.php b/src/Aggregation/TopHits.php
index 18edf4724a..515ffda442 100644
--- a/src/Aggregation/TopHits.php
+++ b/src/Aggregation/TopHits.php
@@ -58,7 +58,7 @@ public function setSort(array $sortArgs): self
     /**
      * Allows to control how the _source field is returned with every hit.
      *
-     * @param array|string|bool $params Fields to be returned or false to disable source
+     * @param array|bool|string $params Fields to be returned or false to disable source
      *
      * @return $this
      */
diff --git a/src/Bulk.php b/src/Bulk.php
index e881897ec9..ba7b09db6e 100644
--- a/src/Bulk.php
+++ b/src/Bulk.php
@@ -45,8 +45,13 @@ public function __construct(Client $client)
         $this->_client = $client;
     }
 
+    public function __toString(): string
+    {
+        return $this->toString();
+    }
+
     /**
-     * @param string|Index $index
+     * @param Index|string $index
      *
      * @return $this
      */
@@ -153,6 +158,7 @@ public function addScript(AbstractScript $script, ?string $opType = null): self
 
     /**
      * @param Document[] $scripts
+     * @param mixed|null $opType
      *
      * @return $this
      */
@@ -166,7 +172,7 @@ public function addScripts(array $scripts, $opType = null): self
     }
 
     /**
-     * @param \Elastica\Script\AbstractScript|\Elastica\Document|array $data
+     * @param array|\Elastica\Document|\Elastica\Script\AbstractScript $data
      *
      * @return $this
      */
@@ -254,11 +260,6 @@ public function setShardTimeout(string $time): self
         return $this->setRequestParam('timeout', $time);
     }
 
-    public function __toString(): string
-    {
-        return $this->toString();
-    }
-
     public function toString(): string
     {
         $data = '';
diff --git a/src/Bulk/Action.php b/src/Bulk/Action.php
index 350a4bc620..d6a435eb49 100644
--- a/src/Bulk/Action.php
+++ b/src/Bulk/Action.php
@@ -106,7 +106,7 @@ public function hasSource(): bool
     }
 
     /**
-     * @param string|Index $index
+     * @param Index|string $index
      *
      * @return $this
      */
@@ -131,7 +131,7 @@ public function setId(string $id): self
     }
 
     /**
-     * @param string|int $routing
+     * @param int|string $routing
      *
      * @return $this
      */
diff --git a/src/Bulk/Action/AbstractDocument.php b/src/Bulk/Action/AbstractDocument.php
index 4ae9cca76c..b149657a6e 100644
--- a/src/Bulk/Action/AbstractDocument.php
+++ b/src/Bulk/Action/AbstractDocument.php
@@ -10,12 +10,12 @@
 abstract class AbstractDocument extends Action
 {
     /**
-     * @var Document|AbstractScript
+     * @var AbstractScript|Document
      */
     protected $_data;
 
     /**
-     * @param Document|AbstractScript $document
+     * @param AbstractScript|Document $document
      */
     public function __construct($document)
     {
@@ -102,21 +102,19 @@ public function getScript()
     }
 
     /**
-     * @return Document|AbstractScript
+     * @return AbstractScript|Document
      */
     public function getData()
     {
         return $this->_data;
     }
 
-    abstract protected function _getMetadata(AbstractUpdateAction $source): array;
-
     /**
      * Creates a bulk action for a document or a script.
      *
      * The action can be index, update, create or delete based on the $opType param (by default index).
      *
-     * @param Document|AbstractScript $data
+     * @param AbstractScript|Document $data
      * @param string                  $opType
      *
      * @return static
@@ -162,4 +160,6 @@ public static function create($data, ?string $opType = null): self
 
         return $action;
     }
+
+    abstract protected function _getMetadata(AbstractUpdateAction $source): array;
 }
diff --git a/src/Bulk/ResponseSet.php b/src/Bulk/ResponseSet.php
index f06af62c34..344d40f2d9 100644
--- a/src/Bulk/ResponseSet.php
+++ b/src/Bulk/ResponseSet.php
@@ -94,7 +94,7 @@ public function current(): Response
     /**
      * {@inheritdoc}
      */
-    public function next()
+    public function next(): void
     {
         ++$this->_position;
     }
@@ -118,7 +118,7 @@ public function valid(): bool
     /**
      * {@inheritdoc}
      */
-    public function rewind()
+    public function rewind(): void
     {
         $this->_position = 0;
     }
diff --git a/src/Client.php b/src/Client.php
index c2c021d680..9a570fd53c 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -95,60 +95,6 @@ public function getVersion(): string
         return $this->_version = $data['version']['number'];
     }
 
-    /**
-     * Inits the client connections.
-     */
-    protected function _initConnections(): void
-    {
-        $connections = [];
-
-        foreach ($this->getConfig('connections') as $connection) {
-            $connections[] = Connection::create($this->_prepareConnectionParams($connection));
-        }
-
-        if ($this->_config->has('servers')) {
-            $servers = $this->_config->get('servers');
-            foreach ($servers as $server) {
-                $connections[] = Connection::create($this->_prepareConnectionParams($server));
-            }
-        }
-
-        // If no connections set, create default connection
-        if (empty($connections)) {
-            $connections[] = Connection::create($this->_prepareConnectionParams($this->getConfig()));
-        }
-
-        if (!$this->_config->has('connectionStrategy')) {
-            if (true === $this->getConfig('roundRobin')) {
-                $this->setConfigValue('connectionStrategy', 'RoundRobin');
-            } else {
-                $this->setConfigValue('connectionStrategy', 'Simple');
-            }
-        }
-
-        $strategy = Connection\Strategy\StrategyFactory::create($this->getConfig('connectionStrategy'));
-
-        $this->_connectionPool = new Connection\ConnectionPool($connections, $strategy, $this->_callback);
-    }
-
-    /**
-     * Creates a Connection params array from a Client or server config array.
-     */
-    protected function _prepareConnectionParams(array $config): array
-    {
-        $params = [];
-        $params['config'] = [];
-        foreach ($config as $key => $value) {
-            if (\in_array($key, ['bigintConversion', 'curl', 'headers', 'url'])) {
-                $params['config'][$key] = $value;
-            } else {
-                $params[$key] = $value;
-            }
-        }
-
-        return $params;
-    }
-
     /**
      * Sets specific config values (updates and keeps default values).
      *
@@ -308,7 +254,7 @@ public function addDocuments(array $docs, array $requestParams = []): ResponseSe
      * Update document, using update script. Requires elasticsearch >= 0.19.0.
      *
      * @param int|string                                               $id      document id
-     * @param array|\Elastica\Script\AbstractScript|\Elastica\Document $data    raw data for request body
+     * @param array|\Elastica\Document|\Elastica\Script\AbstractScript $data    raw data for request body
      * @param string                                                   $index   index to update
      * @param array                                                    $options array of query params to use for query. For possible options check es api
      *
@@ -490,8 +436,8 @@ public function setConnections(array $connections)
      * @see https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-bulk.html
      *
      * @param array                  $ids     Document ids
-     * @param string|\Elastica\Index $index   Index name
-     * @param string|bool            $routing Optional routing key for all ids
+     * @param \Elastica\Index|string $index   Index name
+     * @param bool|string            $routing Optional routing key for all ids
      *
      * @throws InvalidException
      */
@@ -563,7 +509,7 @@ public function bulk(array $params): ResponseSet
      * @param array        $query       OPTIONAL Query params
      * @param string       $contentType Content-Type sent with this request
      *
-     * @throws Exception\ConnectionException|Exception\ClientException
+     * @throws Exception\ClientException|Exception\ConnectionException
      */
     public function request(string $path, string $method = Request::GET, $data = [], array $query = [], string $contentType = Request::DEFAULT_CONTENT_TYPE): Response
     {
@@ -657,4 +603,58 @@ public function setLogger(LoggerInterface $logger)
 
         return $this;
     }
+
+    /**
+     * Inits the client connections.
+     */
+    protected function _initConnections(): void
+    {
+        $connections = [];
+
+        foreach ($this->getConfig('connections') as $connection) {
+            $connections[] = Connection::create($this->_prepareConnectionParams($connection));
+        }
+
+        if ($this->_config->has('servers')) {
+            $servers = $this->_config->get('servers');
+            foreach ($servers as $server) {
+                $connections[] = Connection::create($this->_prepareConnectionParams($server));
+            }
+        }
+
+        // If no connections set, create default connection
+        if (empty($connections)) {
+            $connections[] = Connection::create($this->_prepareConnectionParams($this->getConfig()));
+        }
+
+        if (!$this->_config->has('connectionStrategy')) {
+            if (true === $this->getConfig('roundRobin')) {
+                $this->setConfigValue('connectionStrategy', 'RoundRobin');
+            } else {
+                $this->setConfigValue('connectionStrategy', 'Simple');
+            }
+        }
+
+        $strategy = Connection\Strategy\StrategyFactory::create($this->getConfig('connectionStrategy'));
+
+        $this->_connectionPool = new Connection\ConnectionPool($connections, $strategy, $this->_callback);
+    }
+
+    /**
+     * Creates a Connection params array from a Client or server config array.
+     */
+    protected function _prepareConnectionParams(array $config): array
+    {
+        $params = [];
+        $params['config'] = [];
+        foreach ($config as $key => $value) {
+            if (\in_array($key, ['bigintConversion', 'curl', 'headers', 'url'])) {
+                $params['config'][$key] = $value;
+            } else {
+                $params[$key] = $value;
+            }
+        }
+
+        return $params;
+    }
 }
diff --git a/src/Cluster/Health.php b/src/Cluster/Health.php
index eff20979c8..1e54bcac8d 100644
--- a/src/Cluster/Health.php
+++ b/src/Cluster/Health.php
@@ -30,19 +30,6 @@ public function __construct(Client $client)
         $this->refresh();
     }
 
-    /**
-     * Retrieves the health data from the cluster.
-     */
-    protected function _retrieveHealthData(): array
-    {
-        $endpoint = new \Elasticsearch\Endpoints\Cluster\Health();
-        $endpoint->setParams(['level' => 'shards']);
-
-        $response = $this->_client->requestEndpoint($endpoint);
-
-        return $response->getData();
-    }
-
     /**
      * Gets the health data.
      */
@@ -185,4 +172,17 @@ public function getIndices(): array
 
         return $indices;
     }
+
+    /**
+     * Retrieves the health data from the cluster.
+     */
+    protected function _retrieveHealthData(): array
+    {
+        $endpoint = new \Elasticsearch\Endpoints\Cluster\Health();
+        $endpoint->setParams(['level' => 'shards']);
+
+        $response = $this->_client->requestEndpoint($endpoint);
+
+        return $response->getData();
+    }
 }
diff --git a/src/Connection.php b/src/Connection.php
index 2d23266e23..3a155c4cf7 100644
--- a/src/Connection.php
+++ b/src/Connection.php
@@ -125,7 +125,7 @@ public function setProxy($proxy)
     }
 
     /**
-     * @return string|array
+     * @return array|string
      */
     public function getTransport()
     {
@@ -133,7 +133,7 @@ public function getTransport()
     }
 
     /**
-     * @param string|array $transport
+     * @param array|string $transport
      *
      * @return $this
      */
@@ -321,7 +321,7 @@ public function getConfig($key = '')
     }
 
     /**
-     * @param \Elastica\Connection|array $params Params to create a connection
+     * @param array|\Elastica\Connection $params Params to create a connection
      *
      * @throws Exception\InvalidException
      *
diff --git a/src/Connection/ConnectionPool.php b/src/Connection/ConnectionPool.php
index 5023385bf5..7998099f3e 100644
--- a/src/Connection/ConnectionPool.php
+++ b/src/Connection/ConnectionPool.php
@@ -86,7 +86,7 @@ public function getConnection(): Connection
         return $this->_strategy->getConnection($this->getConnections());
     }
 
-    public function onFail(Connection $connection, Exception $e, Client $client)
+    public function onFail(Connection $connection, Exception $e, Client $client): void
     {
         $connection->setEnabled(false);
 
diff --git a/src/Connection/Strategy/StrategyFactory.php b/src/Connection/Strategy/StrategyFactory.php
index b48a68bc48..971c9492ba 100644
--- a/src/Connection/Strategy/StrategyFactory.php
+++ b/src/Connection/Strategy/StrategyFactory.php
@@ -12,7 +12,7 @@
 class StrategyFactory
 {
     /**
-     * @param mixed|callable|string|StrategyInterface $strategyName
+     * @param callable|mixed|StrategyInterface|string $strategyName
      *
      * @throws InvalidException
      */
diff --git a/src/Document.php b/src/Document.php
index c615c65532..9306ba639a 100644
--- a/src/Document.php
+++ b/src/Document.php
@@ -58,7 +58,7 @@ public function __get(string $key)
     /**
      * @param mixed $value
      */
-    public function __set(string $key, $value)
+    public function __set(string $key, $value): void
     {
         $this->set($key, $value);
     }
@@ -68,7 +68,7 @@ public function __isset(string $key): bool
         return $this->has($key) && null !== $this->get($key);
     }
 
-    public function __unset(string $key)
+    public function __unset(string $key): void
     {
         $this->remove($key);
     }
@@ -76,6 +76,8 @@ public function __unset(string $key)
     /**
      * Get the value of the given field.
      *
+     * @param mixed $key
+     *
      * @throws InvalidException If the given field does not exist
      *
      * @return mixed
diff --git a/src/Exception/Bulk/Response/ActionException.php b/src/Exception/Bulk/Response/ActionException.php
index d69fd08846..a7d57bc603 100644
--- a/src/Exception/Bulk/Response/ActionException.php
+++ b/src/Exception/Bulk/Response/ActionException.php
@@ -50,6 +50,6 @@ public function getErrorMessage(BulkResponse $response): string
             $path .= '/'.$data['_id'];
         }
 
-        return "$opType: $path caused $error";
+        return "{$opType}: {$path} caused {$error}";
     }
 }
diff --git a/src/Exception/Bulk/ResponseException.php b/src/Exception/Bulk/ResponseException.php
index 361e7348f2..7e6b304cc9 100644
--- a/src/Exception/Bulk/ResponseException.php
+++ b/src/Exception/Bulk/ResponseException.php
@@ -34,17 +34,6 @@ public function __construct(ResponseSet $responseSet)
         parent::__construct($message);
     }
 
-    protected function _init(ResponseSet $responseSet)
-    {
-        $this->_responseSet = $responseSet;
-
-        foreach ($responseSet->getBulkResponses() as $bulkResponse) {
-            if ($bulkResponse->hasError()) {
-                $this->_actionExceptions[] = new ActionException($bulkResponse);
-            }
-        }
-    }
-
     /**
      * Returns bulk response set object.
      */
@@ -86,4 +75,15 @@ public function getActionExceptionsAsString(): string
 
         return $message;
     }
+
+    protected function _init(ResponseSet $responseSet): void
+    {
+        $this->_responseSet = $responseSet;
+
+        foreach ($responseSet->getBulkResponses() as $bulkResponse) {
+            if ($bulkResponse->hasError()) {
+                $this->_actionExceptions[] = new ActionException($bulkResponse);
+            }
+        }
+    }
 }
diff --git a/src/Exception/ElasticsearchException.php b/src/Exception/ElasticsearchException.php
index 707d6bdf21..ddb06d15ee 100644
--- a/src/Exception/ElasticsearchException.php
+++ b/src/Exception/ElasticsearchException.php
@@ -13,6 +13,11 @@ class ElasticsearchException extends \Exception implements ExceptionInterface
 {
     public const REMOTE_TRANSPORT_EXCEPTION = 'RemoteTransportException';
 
+    /**
+     * @var array Error array
+     */
+    protected $_error = [];
+
     /**
      * @var string|null Elasticsearch exception name
      */
@@ -23,11 +28,6 @@ class ElasticsearchException extends \Exception implements ExceptionInterface
      */
     private $_isRemote = false;
 
-    /**
-     * @var array Error array
-     */
-    protected $_error = [];
-
     /**
      * Constructs elasticsearch exception.
      *
@@ -40,12 +40,38 @@ public function __construct(int $code, string $error)
         parent::__construct($error, $code);
     }
 
+    /**
+     * Returns elasticsearch exception name.
+     *
+     * @return string|null
+     */
+    public function getExceptionName()
+    {
+        return $this->_exception;
+    }
+
+    /**
+     * Returns whether exception was local to server node or remote.
+     */
+    public function isRemoteTransportException(): bool
+    {
+        return $this->_isRemote;
+    }
+
+    /**
+     * @return array Error array
+     */
+    public function getError(): array
+    {
+        return $this->_error;
+    }
+
     /**
      * Parse error message from elasticsearch.
      *
      * @param string $error Error message
      */
-    protected function _parseError(string $error)
+    protected function _parseError(string $error): void
     {
         $errors = \explode(']; nested: ', $error);
 
@@ -74,30 +100,4 @@ protected function _extractException(string $error)
 
         return null;
     }
-
-    /**
-     * Returns elasticsearch exception name.
-     *
-     * @return string|null
-     */
-    public function getExceptionName()
-    {
-        return $this->_exception;
-    }
-
-    /**
-     * Returns whether exception was local to server node or remote.
-     */
-    public function isRemoteTransportException(): bool
-    {
-        return $this->_isRemote;
-    }
-
-    /**
-     * @return array Error array
-     */
-    public function getError(): array
-    {
-        return $this->_error;
-    }
 }
diff --git a/src/Index.php b/src/Index.php
index ad297a03cd..02df3fddf7 100644
--- a/src/Index.php
+++ b/src/Index.php
@@ -154,7 +154,7 @@ public function updateDocuments(array $docs, array $options = []): ResponseSet
     /**
      * Update entries in the db based on a query.
      *
-     * @param Query|string|array $query   Query object or array
+     * @param array|Query|string $query   Query object or array
      * @param AbstractScript     $script  Script
      * @param array              $options Optional params
      *
@@ -299,7 +299,7 @@ public function deleteById(string $id, array $options = []): Response
     /**
      * Deletes documents matching the given query.
      *
-     * @param Query|AbstractQuery|string|array $query   Query object or array
+     * @param AbstractQuery|array|Query|string $query   Query object or array
      * @param array                            $options Optional params
      *
      * @see https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-delete-by-query.html
@@ -372,7 +372,7 @@ public function refresh(): Response
      * @see https://www.elastic.co/guide/en/elasticsearch/reference/current/indices-create-index.html
      *
      * @param array      $args    Additional arguments to pass to the Create endpoint
-     * @param bool|array $options OPTIONAL
+     * @param array|bool $options OPTIONAL
      *                            bool=> Deletes index first if already exists (default = false).
      *                            array => Associative array of options (option=>value)
      *
@@ -423,8 +423,8 @@ public function exists(): bool
     }
 
     /**
-     * @param string|array|Query $query
-     * @param int|array          $options
+     * @param array|Query|string $query
+     * @param array|int          $options
      * @param BuilderInterface   $builder
      */
     public function createSearch($query = '', $options = null, ?BuilderInterface $builder = null): Search
@@ -439,8 +439,8 @@ public function createSearch($query = '', $options = null, ?BuilderInterface $bu
     /**
      * Searches in this index.
      *
-     * @param string|array|Query $query   Array with all query data inside or a Elastica\Query object
-     * @param int|array          $options Limit or associative array of options (option=>value)
+     * @param array|Query|string $query   Array with all query data inside or a Elastica\Query object
+     * @param array|int          $options Limit or associative array of options (option=>value)
      * @param string             $method  Request method, see Request's constants
      *
      * @see \Elastica\SearchableInterface::search
@@ -455,7 +455,7 @@ public function search($query = '', $options = null, string $method = Request::P
     /**
      * Counts results of query.
      *
-     * @param string|array|Query $query  Array with all query data inside or a Elastica\Query object
+     * @param array|Query|string $query  Array with all query data inside or a Elastica\Query object
      * @param string             $method Request method, see Request's constants
      *
      * @see \Elastica\SearchableInterface::count
@@ -668,7 +668,7 @@ public function analyze(array $body, $args = []): array
      *
      * @see https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-update.html
      *
-     * @param Document|AbstractScript $data    Document or Script with update data
+     * @param AbstractScript|Document $data    Document or Script with update data
      * @param array                   $options array of query params to use for query
      */
     public function updateDocument($data, array $options = []): Response
diff --git a/src/Index/Recovery.php b/src/Index/Recovery.php
index c7ba52d919..e3afb33e60 100644
--- a/src/Index/Recovery.php
+++ b/src/Index/Recovery.php
@@ -77,18 +77,6 @@ public function getData(): array
         return $this->_data;
     }
 
-    /**
-     * @return mixed
-     */
-    protected function getRecoveryData()
-    {
-        $endpoint = new RecoveryEndpoint();
-
-        $this->_response = $this->getIndex()->requestEndpoint($endpoint);
-
-        return $this->getResponse()->getData();
-    }
-
     /**
      * Retrieve the Recovery data.
      *
@@ -100,4 +88,16 @@ public function refresh(): self
 
         return $this;
     }
+
+    /**
+     * @return mixed
+     */
+    protected function getRecoveryData()
+    {
+        $endpoint = new RecoveryEndpoint();
+
+        $this->_response = $this->getIndex()->requestEndpoint($endpoint);
+
+        return $this->getResponse()->getData();
+    }
 }
diff --git a/src/Index/Stats.php b/src/Index/Stats.php
index a1e2157361..99fb7d519a 100644
--- a/src/Index/Stats.php
+++ b/src/Index/Stats.php
@@ -100,7 +100,7 @@ public function getResponse(): Response
     /**
      * Reloads all status data of this object.
      */
-    public function refresh()
+    public function refresh(): void
     {
         $this->_response = $this->getIndex()->requestEndpoint(new \Elasticsearch\Endpoints\Indices\Stats());
         $this->_data = $this->getResponse()->getData();
diff --git a/src/IndexTemplate.php b/src/IndexTemplate.php
index f766ad1860..3025842cfd 100644
--- a/src/IndexTemplate.php
+++ b/src/IndexTemplate.php
@@ -52,9 +52,7 @@ public function __construct(Client $client, $name)
      */
     public function delete()
     {
-        $response = $this->request(Request::DELETE);
-
-        return $response;
+        return $this->request(Request::DELETE);
     }
 
     /**
diff --git a/src/Multi/ResultSet.php b/src/Multi/ResultSet.php
index c3af9502a0..b216430247 100644
--- a/src/Multi/ResultSet.php
+++ b/src/Multi/ResultSet.php
@@ -88,7 +88,7 @@ public function current()
     /**
      * {@inheritdoc}
      */
-    public function next()
+    public function next(): void
     {
         ++$this->_position;
     }
@@ -112,7 +112,7 @@ public function valid(): bool
     /**
      * {@inheritdoc}
      */
-    public function rewind()
+    public function rewind(): void
     {
         $this->_position = 0;
     }
@@ -144,7 +144,7 @@ public function offsetGet($offset)
     /**
      * {@inheritdoc}
      */
-    public function offsetSet($offset, $value)
+    public function offsetSet($offset, $value): void
     {
         if (null === $offset) {
             $this->_resultSets[] = $value;
@@ -156,7 +156,7 @@ public function offsetSet($offset, $value)
     /**
      * {@inheritdoc}
      */
-    public function offsetUnset($offset)
+    public function offsetUnset($offset): void
     {
         unset($this->_resultSets[$offset]);
     }
diff --git a/src/Multi/Search.php b/src/Multi/Search.php
index 8a4b444776..851141eac7 100644
--- a/src/Multi/Search.php
+++ b/src/Multi/Search.php
@@ -16,6 +16,20 @@
  */
 class Search
 {
+    /**
+     * @var Client
+     */
+    protected $_client;
+
+    /**
+     * @var array
+     */
+    protected $_options = [];
+
+    /**
+     * @var BaseSearch[]
+     */
+    protected $_searches = [];
     /**
      * @const string[] valid header options
      */
@@ -32,21 +46,6 @@ class Search
      */
     private $_builder;
 
-    /**
-     * @var Client
-     */
-    protected $_client;
-
-    /**
-     * @var array
-     */
-    protected $_options = [];
-
-    /**
-     * @var BaseSearch[]
-     */
-    protected $_searches = [];
-
     /**
      * Constructs search object.
      */
@@ -139,7 +138,7 @@ public function search(): ResultSet
             Request::POST,
             $data,
             $this->_options,
-        Request::NDJSON_CONTENT_TYPE
+            Request::NDJSON_CONTENT_TYPE
         );
 
         return $this->_builder->buildMultiResultSet($response, $this->getSearches());
diff --git a/src/Param.php b/src/Param.php
index 5fd5450ce4..705d96ac60 100644
--- a/src/Param.php
+++ b/src/Param.php
@@ -45,55 +45,6 @@ public function toArray()
         return $this->_convertArrayable($data);
     }
 
-    /**
-     * Cast objects to arrays.
-     *
-     * @return array
-     */
-    protected function _convertArrayable(array $array)
-    {
-        $arr = [];
-
-        foreach ($array as $key => $value) {
-            if ($value instanceof ArrayableInterface) {
-                $arr[$value instanceof NameableInterface ? $value->getName() : $key] = $value->toArray();
-            } elseif (\is_array($value)) {
-                $arr[$key] = $this->_convertArrayable($value);
-            } else {
-                $arr[$key] = $value;
-            }
-        }
-
-        return $arr;
-    }
-
-    /**
-     * Param's name
-     * Picks the last part of the class name and makes it snake_case
-     * You can override this method if you want to change the name.
-     *
-     * @return string name
-     */
-    protected function _getBaseName()
-    {
-        return Util::getParamName($this);
-    }
-
-    /**
-     * Sets params not inside params array.
-     *
-     * @param string $key
-     * @param mixed  $value
-     *
-     * @return $this
-     */
-    protected function _setRawParam($key, $value)
-    {
-        $this->_rawParams[$key] = $value;
-
-        return $this;
-    }
-
     /**
      * Sets (overwrites) the value at the given key.
      *
@@ -189,4 +140,53 @@ public function count()
     {
         return \count($this->_params);
     }
+
+    /**
+     * Cast objects to arrays.
+     *
+     * @return array
+     */
+    protected function _convertArrayable(array $array)
+    {
+        $arr = [];
+
+        foreach ($array as $key => $value) {
+            if ($value instanceof ArrayableInterface) {
+                $arr[$value instanceof NameableInterface ? $value->getName() : $key] = $value->toArray();
+            } elseif (\is_array($value)) {
+                $arr[$key] = $this->_convertArrayable($value);
+            } else {
+                $arr[$key] = $value;
+            }
+        }
+
+        return $arr;
+    }
+
+    /**
+     * Param's name
+     * Picks the last part of the class name and makes it snake_case
+     * You can override this method if you want to change the name.
+     *
+     * @return string name
+     */
+    protected function _getBaseName()
+    {
+        return Util::getParamName($this);
+    }
+
+    /**
+     * Sets params not inside params array.
+     *
+     * @param string $key
+     * @param mixed  $value
+     *
+     * @return $this
+     */
+    protected function _setRawParam($key, $value)
+    {
+        $this->_rawParams[$key] = $value;
+
+        return $this;
+    }
 }
diff --git a/src/Processor/Append.php b/src/Processor/Append.php
index 06ef8248f7..54f0c74ea5 100644
--- a/src/Processor/Append.php
+++ b/src/Processor/Append.php
@@ -15,7 +15,7 @@ class Append extends AbstractProcessor
      * Append constructor.
      *
      * @param string       $field field name
-     * @param string|array $value field values to append
+     * @param array|string $value field values to append
      */
     public function __construct(string $field, $value)
     {
@@ -36,7 +36,7 @@ public function setField(string $field): self
     /**
      * Set field value.
      *
-     * @param string|array $value
+     * @param array|string $value
      *
      * @return $this
      */
diff --git a/src/Processor/Remove.php b/src/Processor/Remove.php
index a6532684e2..600a60a6c9 100644
--- a/src/Processor/Remove.php
+++ b/src/Processor/Remove.php
@@ -14,7 +14,7 @@ class Remove extends AbstractProcessor
     /**
      * Remove constructor.
      *
-     * @param string|array $field
+     * @param array|string $field
      */
     public function __construct($field)
     {
@@ -24,7 +24,7 @@ public function __construct($field)
     /**
      * Set field.
      *
-     * @param string|array $field
+     * @param array|string $field
      *
      * @return $this
      */
diff --git a/src/Query.php b/src/Query.php
index 0fd6b38871..947954d224 100644
--- a/src/Query.php
+++ b/src/Query.php
@@ -30,7 +30,7 @@ class Query extends Param
     /**
      * Creates a query object.
      *
-     * @param array|AbstractQuery $query Query object (default = null)
+     * @param AbstractQuery|array $query Query object (default = null)
      */
     public function __construct($query = null)
     {
@@ -95,8 +95,8 @@ public function setQuery(AbstractQuery $query): self
     /**
      * Gets the query object.
      *
-     * @return array|AbstractQuery
-     **/
+     * @return AbstractQuery|array
+     */
     public function getQuery()
     {
         return $this->getParam('query');
@@ -361,7 +361,7 @@ public function setSource($params): self
     /**
      * Sets a post_filter to the current query.
      *
-     * @param array|AbstractQuery $filter
+     * @param AbstractQuery|array $filter
      *
      * @see https://www.elastic.co/guide/en/elasticsearch/reference/current/search-request-body.html#request-body-search-post-filter
      */
diff --git a/src/Query/AbstractGeoDistance.php b/src/Query/AbstractGeoDistance.php
index 1a07e2721c..371e217322 100644
--- a/src/Query/AbstractGeoDistance.php
+++ b/src/Query/AbstractGeoDistance.php
@@ -143,6 +143,16 @@ public function setGeohash(string $geohash): self
         return $this;
     }
 
+    /**
+     * {@inheritdoc}
+     */
+    public function toArray(): array
+    {
+        $this->setParam($this->_key, $this->_getLocationData());
+
+        return parent::toArray();
+    }
+
     /**
      * @throws InvalidException
      *
@@ -172,14 +182,4 @@ protected function _getLocationData()
 
         return $location;
     }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function toArray(): array
-    {
-        $this->setParam($this->_key, $this->_getLocationData());
-
-        return parent::toArray();
-    }
 }
diff --git a/src/Query/BoolQuery.php b/src/Query/BoolQuery.php
index 49223c9242..2c87f53abd 100644
--- a/src/Query/BoolQuery.php
+++ b/src/Query/BoolQuery.php
@@ -59,25 +59,6 @@ public function addFilter(AbstractQuery $filter): self
         return $this->addParam('filter', $filter);
     }
 
-    /**
-     * Adds a query to the current object.
-     *
-     * @param string              $type Query type
-     * @param AbstractQuery|array $args Query
-     *
-     * @throws InvalidException If not valid query
-     *
-     * @return $this
-     */
-    protected function _addQuery(string $type, $args): self
-    {
-        if (!\is_array($args) && !($args instanceof AbstractQuery)) {
-            throw new InvalidException('Invalid parameter. Has to be array or instance of Elastica\Query\AbstractQuery');
-        }
-
-        return $this->addParam($type, $args);
-    }
-
     /**
      * Sets boost value of this query.
      *
@@ -113,4 +94,23 @@ public function toArray(): array
 
         return parent::toArray();
     }
+
+    /**
+     * Adds a query to the current object.
+     *
+     * @param string              $type Query type
+     * @param AbstractQuery|array $args Query
+     *
+     * @throws InvalidException If not valid query
+     *
+     * @return $this
+     */
+    protected function _addQuery(string $type, $args): self
+    {
+        if (!\is_array($args) && !($args instanceof AbstractQuery)) {
+            throw new InvalidException('Invalid parameter. Has to be array or instance of Elastica\Query\AbstractQuery');
+        }
+
+        return $this->addParam($type, $args);
+    }
 }
diff --git a/src/Query/DistanceFeature.php b/src/Query/DistanceFeature.php
index 58c0631856..58d7b19dcf 100644
--- a/src/Query/DistanceFeature.php
+++ b/src/Query/DistanceFeature.php
@@ -22,7 +22,7 @@ public function setField(string $field): self
     }
 
     /**
-     * @param string|array $origin
+     * @param array|string $origin
      */
     public function setOrigin($origin): self
     {
diff --git a/src/Query/FunctionScore.php b/src/Query/FunctionScore.php
index 6c13a317ed..5b4256fb9d 100644
--- a/src/Query/FunctionScore.php
+++ b/src/Query/FunctionScore.php
@@ -64,7 +64,7 @@ public function setQuery(AbstractQuery $query): self
      * Add a function to the function_score query.
      *
      * @param string                     $functionType   valid values are DECAY_* constants and script_score
-     * @param array|float|AbstractScript $functionParams the body of the function. See documentation for proper syntax.
+     * @param AbstractScript|array|float $functionParams the body of the function. See documentation for proper syntax.
      * @param AbstractQuery              $filter         filter to apply to the function
      * @param float                      $weight         function weight
      *
diff --git a/src/Query/HasChild.php b/src/Query/HasChild.php
index 026055d171..23b6c281bb 100644
--- a/src/Query/HasChild.php
+++ b/src/Query/HasChild.php
@@ -16,7 +16,7 @@ class HasChild extends AbstractQuery
     /**
      * Construct HasChild Query.
      *
-     * @param string|BaseQuery|AbstractQuery $query
+     * @param AbstractQuery|BaseQuery|string $query
      * @param string                         $type  Parent document type
      */
     public function __construct($query, ?string $type = null)
@@ -28,7 +28,7 @@ public function __construct($query, ?string $type = null)
     /**
      * Sets query object.
      *
-     * @param string|BaseQuery|AbstractQuery $query
+     * @param AbstractQuery|BaseQuery|string $query
      *
      * @return $this
      */
diff --git a/src/Query/HasParent.php b/src/Query/HasParent.php
index 0c7e69b9f0..ace01427d5 100644
--- a/src/Query/HasParent.php
+++ b/src/Query/HasParent.php
@@ -14,7 +14,7 @@ class HasParent extends AbstractQuery
     /**
      * Construct HasChild Query.
      *
-     * @param string|BaseQuery|AbstractQuery $query
+     * @param AbstractQuery|BaseQuery|string $query
      * @param string                         $type  Parent document type
      */
     public function __construct($query, string $type)
@@ -26,7 +26,7 @@ public function __construct($query, string $type)
     /**
      * Sets query object.
      *
-     * @param string|BaseQuery|AbstractQuery $query
+     * @param AbstractQuery|BaseQuery|string $query
      *
      * @return $this
      */
diff --git a/src/Query/MoreLikeThis.php b/src/Query/MoreLikeThis.php
index 189722f779..572de612eb 100644
--- a/src/Query/MoreLikeThis.php
+++ b/src/Query/MoreLikeThis.php
@@ -26,7 +26,7 @@ public function setFields(array $fields): self
     /**
      * Set the "like" value.
      *
-     * @param string|self $like
+     * @param self|string $like
      *
      * @return $this
      */
@@ -169,8 +169,8 @@ public function toArray(): array
         } elseif (!empty($array['more_like_this']['like']['_source'])) {
             $doc = $array['more_like_this']['like'];
             $doc['doc'] = $array['more_like_this']['like']['_source'];
-            unset($doc['_id']);
-            unset($doc['_source']);
+            unset($doc['_id'], $doc['_source']);
+
             $array['more_like_this']['like'] = $doc;
         }
 
diff --git a/src/Query/ParentId.php b/src/Query/ParentId.php
index 151cc55bc5..098b77761d 100644
--- a/src/Query/ParentId.php
+++ b/src/Query/ParentId.php
@@ -23,17 +23,17 @@ public function __construct(string $type, string $id, bool $ignoreUnmapped = fal
         $this->setIgnoreUnmapped($ignoreUnmapped);
     }
 
-    private function setRelationshipType(string $type)
+    private function setRelationshipType(string $type): void
     {
         $this->setParam('type', $type);
     }
 
-    private function setId(string $id)
+    private function setId(string $id): void
     {
         $this->setParam('id', $id);
     }
 
-    private function setIgnoreUnmapped(bool $ignoreUnmapped = false)
+    private function setIgnoreUnmapped(bool $ignoreUnmapped = false): void
     {
         $this->setParam('ignore_unmapped', $ignoreUnmapped);
     }
diff --git a/src/Query/Percolate.php b/src/Query/Percolate.php
index 97818282e8..e04217cada 100644
--- a/src/Query/Percolate.php
+++ b/src/Query/Percolate.php
@@ -29,7 +29,7 @@ public function setField(string $field): self
     /**
      * The source of the document being percolated.
      *
-     * @param Document|array $document
+     * @param array|Document $document
      *
      * @return $this
      */
diff --git a/src/Query/Prefix.php b/src/Query/Prefix.php
index 340571d1e6..a045fbdb93 100644
--- a/src/Query/Prefix.php
+++ b/src/Query/Prefix.php
@@ -36,7 +36,7 @@ public function setRawPrefix(array $prefix): self
      * Adds a prefix to the prefix query.
      *
      * @param string       $key   Key to query
-     * @param string|array $value Values(s) for the query. Boost can be set with array
+     * @param array|string $value Values(s) for the query. Boost can be set with array
      * @param float        $boost OPTIONAL Boost value (default = 1.0)
      *
      * @return $this
diff --git a/src/Query/Script.php b/src/Query/Script.php
index 9b38c40ec2..2328e60be6 100644
--- a/src/Query/Script.php
+++ b/src/Query/Script.php
@@ -17,7 +17,7 @@ class Script extends AbstractQuery
     /**
      * Construct script query.
      *
-     * @param array|string|AbstractScript $script Script
+     * @param AbstractScript|array|string $script Script
      */
     public function __construct($script = null)
     {
@@ -29,7 +29,7 @@ public function __construct($script = null)
     /**
      * Sets script object.
      *
-     * @param BaseScript|string|array $script
+     * @param array|BaseScript|string $script
      *
      * @return $this
      */
diff --git a/src/Query/SpanTerm.php b/src/Query/SpanTerm.php
index 7fea1dc6dd..8a6d95c306 100644
--- a/src/Query/SpanTerm.php
+++ b/src/Query/SpanTerm.php
@@ -39,7 +39,7 @@ public function setRawTerm(array $term): self
      * Adds a term to the term query.
      *
      * @param string       $key   Key to query
-     * @param string|array $value Values(s) for the query. Boost can be set with array
+     * @param array|string $value Values(s) for the query. Boost can be set with array
      * @param float        $boost OPTIONAL Boost value (default = 1.0)
      *
      * @return $this
diff --git a/src/Query/Term.php b/src/Query/Term.php
index 4bd30703ee..df46dfc745 100644
--- a/src/Query/Term.php
+++ b/src/Query/Term.php
@@ -38,7 +38,7 @@ public function setRawTerm(array $term): self
      * Adds a term to the term query.
      *
      * @param string       $key   Key to query
-     * @param string|array $value Values(s) for the query. Boost can be set with array
+     * @param array|string $value Values(s) for the query. Boost can be set with array
      * @param float        $boost OPTIONAL Boost value (default = 1.0)
      *
      * @return $this
diff --git a/src/QueryBuilder.php b/src/QueryBuilder.php
index 927d135b0a..c1d885da3e 100644
--- a/src/QueryBuilder.php
+++ b/src/QueryBuilder.php
@@ -54,7 +54,7 @@ public function __call(string $dsl, array $arguments): Facade
     /**
      * Adds a new DSL object.
      */
-    public function addDSL(DSL $dsl)
+    public function addDSL(DSL $dsl): void
     {
         $this->_facades[$dsl->getType()] = new Facade($dsl, $this->_version);
     }
diff --git a/src/QueryBuilder/DSL/Aggregation.php b/src/QueryBuilder/DSL/Aggregation.php
index a3ba1b8882..dc5f92f886 100644
--- a/src/QueryBuilder/DSL/Aggregation.php
+++ b/src/QueryBuilder/DSL/Aggregation.php
@@ -176,7 +176,7 @@ public function cardinality(string $name): Cardinality
      *
      * @param string $name
      */
-    public function geo_bounds($name)
+    public function geo_bounds($name): void
     {
         throw new NotImplementedException();
     }
@@ -358,7 +358,7 @@ public function date_histogram(string $name, string $field, $interval): DateHist
      *
      * @param string       $name   the name if this aggregation
      * @param string       $field  the field on which to perform this aggregation
-     * @param string|array $origin the point from which distances will be calculated
+     * @param array|string $origin the point from which distances will be calculated
      */
     public function geo_distance(string $name, string $field, $origin): GeoDistance
     {
diff --git a/src/QueryBuilder/DSL/Query.php b/src/QueryBuilder/DSL/Query.php
index 6cc8a6fff1..a4f72ca7ed 100644
--- a/src/QueryBuilder/DSL/Query.php
+++ b/src/QueryBuilder/DSL/Query.php
@@ -144,7 +144,7 @@ public function dis_max(): DisMax
      *
      * @see https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-distance-feature-query.html
      *
-     * @param string|array $origin
+     * @param array|string $origin
      */
     public function distance_feature(string $field, $origin, string $pivot): DistanceFeature
     {
@@ -210,7 +210,7 @@ public function geo_polygon(string $key, array $points): GeoPolygon
      *
      * @see https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-has-child-query.html
      *
-     * @param string|BaseQuery|AbstractQuery $query
+     * @param AbstractQuery|BaseQuery|string $query
      * @param string                         $type  Parent document type
      */
     public function has_child($query, ?string $type = null): HasChild
@@ -223,7 +223,7 @@ public function has_child($query, ?string $type = null): HasChild
      *
      * @see https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-has-parent-query.html
      *
-     * @param string|BaseQuery|AbstractQuery $query
+     * @param AbstractQuery|BaseQuery|string $query
      * @param string                         $type  Parent document type
      */
     public function has_parent($query, string $type): HasParent
@@ -265,6 +265,8 @@ public function match_none(): MatchNone
      * match phrase query.
      *
      * @see https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-match-query-phrase.html
+     *
+     * @param mixed|null $values
      */
     public function match_phrase(?string $field = null, $values = null): MatchPhrase
     {
@@ -275,6 +277,8 @@ public function match_phrase(?string $field = null, $values = null): MatchPhrase
      * match phrase prefix query.
      *
      * @see https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-match-query-phrase-prefix.html
+     *
+     * @param mixed|null $values
      */
     public function match_phrase_prefix(?string $field = null, $values = null): MatchPhrasePrefix
     {
diff --git a/src/QueryBuilder/Facade.php b/src/QueryBuilder/Facade.php
index 7ba37fde86..0a28cb83e4 100644
--- a/src/QueryBuilder/Facade.php
+++ b/src/QueryBuilder/Facade.php
@@ -8,7 +8,7 @@
  * Facade for a specific DSL object.
  *
  * @author Manuel Andreo Garcia <andreo.garcia@googlemail.com>
- **/
+ */
 class Facade
 {
     /**
diff --git a/src/Reindex.php b/src/Reindex.php
index 17d5e7bc09..9a901f8502 100644
--- a/src/Reindex.php
+++ b/src/Reindex.php
@@ -73,6 +73,68 @@ public function run(): Response
         return $this->_lastResponse;
     }
 
+    public function setWaitForCompletion($value): void
+    {
+        \is_bool($value) && $value = $value ? 'true' : 'false';
+
+        $this->setParam(self::WAIT_FOR_COMPLETION, $value);
+    }
+
+    public function setWaitForActiveShards($value): void
+    {
+        $this->setParam(self::WAIT_FOR_ACTIVE_SHARDS, $value);
+    }
+
+    public function setTimeout($value): void
+    {
+        $this->setParam(self::TIMEOUT, $value);
+    }
+
+    public function setScroll($value): void
+    {
+        $this->setParam(self::SCROLL, $value);
+    }
+
+    public function setRequestsPerSecond($value): void
+    {
+        $this->setParam(self::REQUESTS_PER_SECOND, $value);
+    }
+
+    public function setScript(Script $script): void
+    {
+        $this->setParam(self::SCRIPT, $script);
+    }
+
+    public function setQuery(AbstractQuery $query): void
+    {
+        $this->setParam(self::QUERY, $query);
+    }
+
+    public function setPipeline(Pipeline $pipeline): void
+    {
+        $this->setParam(self::PIPELINE, $pipeline);
+    }
+
+    /**
+     * @param bool|string $value
+     */
+    public function setRefresh($value): void
+    {
+        \is_bool($value) && $value = $value ? self::REFRESH_TRUE : self::REFRESH_FALSE;
+
+        $this->setParam(self::REFRESH, $value);
+    }
+
+    public function getTaskId()
+    {
+        $taskId = null;
+        if ($this->_lastResponse instanceof Response) {
+            $taskId = $this->_lastResponse->getData()['task'] ? $this->_lastResponse->getData()['task'] : null;
+        }
+
+        return $taskId;
+    }
+
     protected function _getBody(Index $oldIndex, Index $newIndex, array $params): array
     {
         $body = \array_merge([
@@ -80,9 +142,7 @@ protected function _getBody(Index $oldIndex, Index $newIndex, array $params): ar
             'dest' => $this->_getDestPartBody($newIndex, $params),
         ], $this->_resolveBodyOptions($params));
 
-        $body = $this->_setBodyScript($body);
-
-        return $body;
+        return $this->_setBodyScript($body);
     }
 
     protected function _getSourcePartBody(Index $index, array $params): array
@@ -91,9 +151,7 @@ protected function _getSourcePartBody(Index $index, array $params): array
             'index' => $index->getName(),
         ], $this->_resolveSourceOptions($params));
 
-        $sourceBody = $this->_setSourceQuery($sourceBody);
-
-        return $sourceBody;
+        return $this->_setSourceQuery($sourceBody);
     }
 
     protected function _getDestPartBody(Index $index, array $params): array
@@ -164,66 +222,4 @@ private function _setBodyScript(array $body): array
 
         return $body;
     }
-
-    public function setWaitForCompletion($value)
-    {
-        \is_bool($value) && $value = $value ? 'true' : 'false';
-
-        $this->setParam(self::WAIT_FOR_COMPLETION, $value);
-    }
-
-    public function setWaitForActiveShards($value)
-    {
-        $this->setParam(self::WAIT_FOR_ACTIVE_SHARDS, $value);
-    }
-
-    public function setTimeout($value)
-    {
-        $this->setParam(self::TIMEOUT, $value);
-    }
-
-    public function setScroll($value)
-    {
-        $this->setParam(self::SCROLL, $value);
-    }
-
-    public function setRequestsPerSecond($value)
-    {
-        $this->setParam(self::REQUESTS_PER_SECOND, $value);
-    }
-
-    public function setScript(Script $script)
-    {
-        $this->setParam(self::SCRIPT, $script);
-    }
-
-    public function setQuery(AbstractQuery $query): void
-    {
-        $this->setParam(self::QUERY, $query);
-    }
-
-    public function setPipeline(Pipeline $pipeline): void
-    {
-        $this->setParam(self::PIPELINE, $pipeline);
-    }
-
-    /**
-     * @param bool|string $value
-     */
-    public function setRefresh($value): void
-    {
-        \is_bool($value) && $value = $value ? self::REFRESH_TRUE : self::REFRESH_FALSE;
-
-        $this->setParam(self::REFRESH, $value);
-    }
-
-    public function getTaskId()
-    {
-        $taskId = null;
-        if ($this->_lastResponse instanceof Response) {
-            $taskId = $this->_lastResponse->getData()['task'] ? $this->_lastResponse->getData()['task'] : null;
-        }
-
-        return $taskId;
-    }
 }
diff --git a/src/Request.php b/src/Request.php
index 8b81b21e6b..1577b9cc20 100644
--- a/src/Request.php
+++ b/src/Request.php
@@ -46,6 +46,14 @@ public function __construct(string $path, string $method = self::GET, $data = []
         $this->setContentType($contentType);
     }
 
+    /**
+     * @return string
+     */
+    public function __toString()
+    {
+        return $this->toString();
+    }
+
     /**
      * Sets the request method. Use one of the for consts.
      *
@@ -195,12 +203,4 @@ public function toString()
     {
         return JSON::stringify($this->toArray());
     }
-
-    /**
-     * @return string
-     */
-    public function __toString()
-    {
-        return $this->toString();
-    }
 }
diff --git a/src/Rescore/AbstractRescore.php b/src/Rescore/AbstractRescore.php
index a753351f9b..5d6e8dd4b1 100644
--- a/src/Rescore/AbstractRescore.php
+++ b/src/Rescore/AbstractRescore.php
@@ -14,22 +14,22 @@
 abstract class AbstractRescore extends Param
 {
     /**
-     * Overridden to return rescore as name.
+     * Sets window_size.
      *
-     * @return string name
+     * @return $this
      */
-    protected function _getBaseName(): string
+    public function setWindowSize(int $size): AbstractRescore
     {
-        return 'rescore';
+        return $this->setParam('window_size', $size);
     }
 
     /**
-     * Sets window_size.
+     * Overridden to return rescore as name.
      *
-     * @return $this
+     * @return string name
      */
-    public function setWindowSize(int $size): AbstractRescore
+    protected function _getBaseName(): string
     {
-        return $this->setParam('window_size', $size);
+        return 'rescore';
     }
 }
diff --git a/src/Rescore/Query.php b/src/Rescore/Query.php
index 8f2c9fc53d..4e50d9eb6a 100644
--- a/src/Rescore/Query.php
+++ b/src/Rescore/Query.php
@@ -16,7 +16,7 @@ class Query extends AbstractRescore
     /**
      * Constructor.
      *
-     * @param string|\Elastica\Query\AbstractQuery $query
+     * @param \Elastica\Query\AbstractQuery|string $query
      */
     public function __construct($query = null)
     {
@@ -50,7 +50,7 @@ public function toArray(): array
     /**
      * Sets rescoreQuery object.
      *
-     * @param string|\Elastica\Query|\Elastica\Query\AbstractQuery $rescoreQuery
+     * @param \Elastica\Query|\Elastica\Query\AbstractQuery|string $rescoreQuery
      *
      * @return $this
      */
diff --git a/src/Response.php b/src/Response.php
index 487e83cb39..baeb3f0375 100644
--- a/src/Response.php
+++ b/src/Response.php
@@ -59,7 +59,7 @@ class Response
     /**
      * Construct.
      *
-     * @param string|array $responseString Response string (json)
+     * @param array|string $responseString Response string (json)
      * @param int          $responseStatus http status code
      */
     public function __construct($responseString, $responseStatus = null)
@@ -349,7 +349,7 @@ public function getScrollId()
      *
      * @param bool $jsonBigintConversion
      */
-    public function setJsonBigintConversion($jsonBigintConversion)
+    public function setJsonBigintConversion($jsonBigintConversion): void
     {
         $this->_jsonBigintConversion = $jsonBigintConversion;
     }
diff --git a/src/Result.php b/src/Result.php
index fca02e691a..1d023475dc 100644
--- a/src/Result.php
+++ b/src/Result.php
@@ -28,6 +28,34 @@ public function __construct(array $hit)
         $this->_hit = $hit;
     }
 
+    /**
+     * Magic function to directly access keys inside the result.
+     *
+     * Returns null if key does not exist
+     *
+     * @param string $key Key name
+     *
+     * @return mixed Key value
+     */
+    public function __get($key)
+    {
+        $source = $this->getData();
+
+        return $source[$key] ?? null;
+    }
+
+    /**
+     * Magic function to support isset() calls.
+     *
+     * @param string $key Key name
+     */
+    public function __isset($key): bool
+    {
+        $source = $this->getData();
+
+        return \array_key_exists($key, $source) && null !== $source[$key];
+    }
+
     /**
      * Returns a param from the result hit array.
      *
@@ -125,7 +153,7 @@ public function getHit(): array
     /**
      * Returns the version information from the hit.
      *
-     * @return string|int Document version
+     * @return int|string Document version
      */
     public function getVersion()
     {
@@ -198,10 +226,8 @@ public function getDocument(): Document
         $doc = new Document();
         $doc->setData($this->getSource());
         $hit = $this->getHit();
-        unset($hit['_source']);
-        unset($hit['_explanation']);
-        unset($hit['highlight']);
-        unset($hit['_score']);
+        unset($hit['_source'], $hit['_explanation'], $hit['highlight'], $hit['_score']);
+
         $doc->setParams($hit);
 
         return $doc;
@@ -212,36 +238,8 @@ public function getDocument(): Document
      *
      * @param mixed $value
      */
-    public function setParam(string $param, $value)
+    public function setParam(string $param, $value): void
     {
         $this->_hit[$param] = $value;
     }
-
-    /**
-     * Magic function to directly access keys inside the result.
-     *
-     * Returns null if key does not exist
-     *
-     * @param string $key Key name
-     *
-     * @return mixed Key value
-     */
-    public function __get($key)
-    {
-        $source = $this->getData();
-
-        return $source[$key] ?? null;
-    }
-
-    /**
-     * Magic function to support isset() calls.
-     *
-     * @param string $key Key name
-     */
-    public function __isset($key): bool
-    {
-        $source = $this->getData();
-
-        return \array_key_exists($key, $source) && null !== $source[$key];
-    }
 }
diff --git a/src/ResultSet/ChainProcessor.php b/src/ResultSet/ChainProcessor.php
index 7fbec9dd2e..723adf6884 100644
--- a/src/ResultSet/ChainProcessor.php
+++ b/src/ResultSet/ChainProcessor.php
@@ -26,7 +26,7 @@ public function __construct(array $processors)
     /**
      * {@inheritdoc}
      */
-    public function process(ResultSet $resultSet)
+    public function process(ResultSet $resultSet): void
     {
         foreach ($this->processors as $processor) {
             $processor->process($resultSet);
diff --git a/src/ResultSet/DefaultBuilder.php b/src/ResultSet/DefaultBuilder.php
index 3dfcdba03f..7dc8f9a3e0 100644
--- a/src/ResultSet/DefaultBuilder.php
+++ b/src/ResultSet/DefaultBuilder.php
@@ -15,9 +15,8 @@ class DefaultBuilder implements BuilderInterface
     public function buildResultSet(Response $response, Query $query): ResultSet
     {
         $results = $this->buildResults($response);
-        $resultSet = new ResultSet($response, $query, $results);
 
-        return $resultSet;
+        return new ResultSet($response, $query, $results);
     }
 
     /**
diff --git a/src/Script/AbstractScript.php b/src/Script/AbstractScript.php
index fbe6f7a61b..2025e8f6b2 100644
--- a/src/Script/AbstractScript.php
+++ b/src/Script/AbstractScript.php
@@ -27,10 +27,29 @@ abstract class AbstractScript extends AbstractUpdateAction
      */
     private $_lang;
 
+    /**
+     * @param string|null $lang       Script language, see constants
+     * @param string|null $documentId Document ID the script action should be performed on (only relevant in update context)
+     */
+    public function __construct(?array $params = null, ?string $lang = null, ?string $documentId = null)
+    {
+        if ($params) {
+            $this->setParams($params);
+        }
+
+        if (null !== $lang) {
+            $this->setLang($lang);
+        }
+
+        if (null !== $documentId) {
+            $this->setId($documentId);
+        }
+    }
+
     /**
      * Factory to create a script object from data structure (reverse toArray).
      *
-     * @param string|array|AbstractScript $data
+     * @param AbstractScript|array|string $data
      *
      * @throws InvalidException
      *
@@ -55,53 +74,6 @@ public static function create($data)
         throw new InvalidException('Failed to create script. Invalid data passed.');
     }
 
-    private static function _createFromArray(array $data)
-    {
-        $params = $data['script']['params'] ?? [];
-        $lang = $data['script']['lang'] ?? null;
-
-        if (!\is_array($params)) {
-            throw new InvalidException('Script params must be an array');
-        }
-
-        if (isset($data['script']['source'])) {
-            return new Script(
-                $data['script']['source'],
-                $params,
-                $lang
-            );
-        }
-
-        if (isset($data['script']['id'])) {
-            return new ScriptId(
-                $data['script']['id'],
-                $params,
-                $lang
-            );
-        }
-
-        throw new InvalidException('Failed to create script. Invalid data passed.');
-    }
-
-    /**
-     * @param string|null $lang       Script language, see constants
-     * @param string|null $documentId Document ID the script action should be performed on (only relevant in update context)
-     */
-    public function __construct(?array $params = null, ?string $lang = null, ?string $documentId = null)
-    {
-        if ($params) {
-            $this->setParams($params);
-        }
-
-        if (null !== $lang) {
-            $this->setLang($lang);
-        }
-
-        if (null !== $documentId) {
-            $this->setId($documentId);
-        }
-    }
-
     public function setLang(string $lang): self
     {
         $this->_lang = $lang;
@@ -114,11 +86,6 @@ public function getLang(): ?string
         return $this->_lang;
     }
 
-    /**
-     * Returns an array with the script type as key and the script content as value.
-     */
-    abstract protected function getScriptTypeArray(): array;
-
     /**
      * {@inheritdoc}
      */
@@ -136,4 +103,37 @@ public function toArray(): array
 
         return ['script' => $array];
     }
+
+    /**
+     * Returns an array with the script type as key and the script content as value.
+     */
+    abstract protected function getScriptTypeArray(): array;
+
+    private static function _createFromArray(array $data)
+    {
+        $params = $data['script']['params'] ?? [];
+        $lang = $data['script']['lang'] ?? null;
+
+        if (!\is_array($params)) {
+            throw new InvalidException('Script params must be an array');
+        }
+
+        if (isset($data['script']['source'])) {
+            return new Script(
+                $data['script']['source'],
+                $params,
+                $lang
+            );
+        }
+
+        if (isset($data['script']['id'])) {
+            return new ScriptId(
+                $data['script']['id'],
+                $params,
+                $lang
+            );
+        }
+
+        throw new InvalidException('Failed to create script. Invalid data passed.');
+    }
 }
diff --git a/src/Script/ScriptFields.php b/src/Script/ScriptFields.php
index 9664daeec0..9dc9fb68d6 100644
--- a/src/Script/ScriptFields.php
+++ b/src/Script/ScriptFields.php
@@ -15,7 +15,7 @@
 class ScriptFields extends Param
 {
     /**
-     * @param Script[]|array $scripts OPTIONAL
+     * @param array|Script[] $scripts OPTIONAL
      */
     public function __construct(array $scripts = [])
     {
@@ -42,7 +42,7 @@ public function addScript(string $name, AbstractScript $script): self
     }
 
     /**
-     * @param Script[]|array $scripts Associative array of string => Elastica\Script\Script
+     * @param array|Script[] $scripts Associative array of string => Elastica\Script\Script
      *
      * @return $this
      */
diff --git a/src/Scroll.php b/src/Scroll.php
index d06a6d4809..c65c25d2b9 100644
--- a/src/Scroll.php
+++ b/src/Scroll.php
@@ -133,7 +133,7 @@ public function rewind(): void
     /**
      * Cleares the search context on ES and marks this Scroll instance as finished.
      */
-    public function clear()
+    public function clear(): void
     {
         if (null !== $this->_nextScrollId) {
             $this->_search->getClient()->request(
@@ -150,7 +150,7 @@ public function clear()
     /**
      * Prepares Scroll for next request.
      */
-    protected function _setScrollId(ResultSet $resultSet)
+    protected function _setScrollId(ResultSet $resultSet): void
     {
         if (0 === $this->currentPage) {
             $this->totalPages = $resultSet->count() > 0 ? \ceil($resultSet->getTotalHits() / $resultSet->count()) : 0;
@@ -170,7 +170,7 @@ protected function _setScrollId(ResultSet $resultSet)
     /**
      * Save all search options manipulated by Scroll.
      */
-    protected function _saveOptions()
+    protected function _saveOptions(): void
     {
         if ($this->_search->hasOption(Search::OPTION_SCROLL)) {
             $this->_options[0] = $this->_search->getOption(Search::OPTION_SCROLL);
@@ -196,7 +196,7 @@ protected function _saveOptions()
     /**
      * Revert search options to previously saved state.
      */
-    protected function _revertOptions()
+    protected function _revertOptions(): void
     {
         $this->_search->setOption(Search::OPTION_SCROLL, $this->_options[0]);
         $this->_search->setOption(Search::OPTION_SCROLL_ID, $this->_options[1]);
diff --git a/src/Search.php b/src/Search.php
index b74e8923c3..ae0372663a 100644
--- a/src/Search.php
+++ b/src/Search.php
@@ -39,11 +39,6 @@ class Search
     public const OPTION_SEARCH_TYPE_SUGGEST = 'suggest';
     public const OPTION_SEARCH_IGNORE_UNAVAILABLE = 'ignore_unavailable';
 
-    /**
-     * @var BuilderInterface|null
-     */
-    private $builder;
-
     /**
      * Array of indices names.
      *
@@ -68,6 +63,11 @@ class Search
      */
     protected $_client;
 
+    /**
+     * @var BuilderInterface|null
+     */
+    private $builder;
+
     /**
      * Constructs search object.
      */
@@ -114,7 +114,7 @@ public function addIndices(array $indices = []): self
     }
 
     /**
-     * @param string|array|Query|Suggest|Query\AbstractQuery $query
+     * @param array|Query|Query\AbstractQuery|string|Suggest $query
      */
     public function setQuery($query): self
     {
@@ -189,34 +189,6 @@ public function getOptions(): array
         return $this->_options;
     }
 
-    /**
-     * @throws InvalidException If the given key is not a valid option
-     */
-    protected function validateOption(string $key): void
-    {
-        switch ($key) {
-            case self::OPTION_SEARCH_TYPE:
-            case self::OPTION_ROUTING:
-            case self::OPTION_PREFERENCE:
-            case self::OPTION_VERSION:
-            case self::OPTION_TIMEOUT:
-            case self::OPTION_FROM:
-            case self::OPTION_SIZE:
-            case self::OPTION_SCROLL:
-            case self::OPTION_SCROLL_ID:
-            case self::OPTION_SEARCH_TYPE_SUGGEST:
-            case self::OPTION_SEARCH_IGNORE_UNAVAILABLE:
-            case self::OPTION_QUERY_CACHE:
-            case self::OPTION_TERMINATE_AFTER:
-            case self::OPTION_SHARD_REQUEST_CACHE:
-            case self::OPTION_FILTER_PATH:
-            case self::OPTION_TYPED_KEYS:
-                return;
-        }
-
-        throw new InvalidException('Invalid option '.$key);
-    }
-
     /**
      * Return client object.
      */
@@ -284,8 +256,8 @@ public function getPath(): string
     /**
      * Search in the set indices.
      *
-     * @param string|array|Query $query
-     * @param int|array          $options Limit or associative array of options (option=>value)
+     * @param array|Query|string $query
+     * @param array|int          $options Limit or associative array of options (option=>value)
      *
      * @throws InvalidException
      */
@@ -312,7 +284,7 @@ public function search($query = '', $options = null, string $method = Request::P
     }
 
     /**
-     * @param string|array|Query $query
+     * @param array|Query|string $query
      * @param bool               $fullResult By default only the total hit count is returned. If set to true, the full ResultSet including aggregations is returned
      *
      * @return int|ResultSet
@@ -341,7 +313,7 @@ public function count($query = '', bool $fullResult = false, string $method = Re
 
     /**
      * @param array|int          $options
-     * @param string|array|Query $query
+     * @param array|Query|string $query
      */
     public function setOptionsAndQuery($options = null, $query = ''): self
     {
@@ -385,4 +357,32 @@ public function getResultSetBuilder(): BuilderInterface
     {
         return $this->builder;
     }
+
+    /**
+     * @throws InvalidException If the given key is not a valid option
+     */
+    protected function validateOption(string $key): void
+    {
+        switch ($key) {
+            case self::OPTION_SEARCH_TYPE:
+            case self::OPTION_ROUTING:
+            case self::OPTION_PREFERENCE:
+            case self::OPTION_VERSION:
+            case self::OPTION_TIMEOUT:
+            case self::OPTION_FROM:
+            case self::OPTION_SIZE:
+            case self::OPTION_SCROLL:
+            case self::OPTION_SCROLL_ID:
+            case self::OPTION_SEARCH_TYPE_SUGGEST:
+            case self::OPTION_SEARCH_IGNORE_UNAVAILABLE:
+            case self::OPTION_QUERY_CACHE:
+            case self::OPTION_TERMINATE_AFTER:
+            case self::OPTION_SHARD_REQUEST_CACHE:
+            case self::OPTION_FILTER_PATH:
+            case self::OPTION_TYPED_KEYS:
+                return;
+        }
+
+        throw new InvalidException('Invalid option '.$key);
+    }
 }
diff --git a/src/SearchableInterface.php b/src/SearchableInterface.php
index 7dcacb870a..8494ecdca5 100644
--- a/src/SearchableInterface.php
+++ b/src/SearchableInterface.php
@@ -25,8 +25,8 @@ interface SearchableInterface
      *      }
      * }
      *
-     * @param string|array|\Elastica\Query $query   Array with all query data inside or a Elastica\Query object
-     * @param int|array                    $options Limit or associative array of options (option=>value)
+     * @param array|\Elastica\Query|string $query   Array with all query data inside or a Elastica\Query object
+     * @param array|int                    $options Limit or associative array of options (option=>value)
      * @param string                       $method  Request method, see Request's constants
      */
     public function search($query = '', $options = null, string $method = Request::POST): ResultSet;
@@ -36,7 +36,7 @@ public function search($query = '', $options = null, string $method = Request::P
      *
      * If no query is set, matchall query is created
      *
-     * @param string|array|\Elastica\Query $query  Array with all query data inside or a Elastica\Query object
+     * @param array|\Elastica\Query|string $query  Array with all query data inside or a Elastica\Query object
      * @param string                       $method Request method, see Request's constants
      *
      * @return int number of documents matching the query
@@ -45,6 +45,7 @@ public function count($query = '', string $method = Request::POST);
 
     /**
      * @param \Elastica\Query|string $query
+     * @param mixed|null             $options
      */
     public function createSearch($query = '', $options = null): Search;
 }
diff --git a/src/Status.php b/src/Status.php
index 5544b6267b..2459bed784 100644
--- a/src/Status.php
+++ b/src/Status.php
@@ -53,7 +53,7 @@ public function __construct(Client $client)
      */
     public function getData()
     {
-        if (\is_null($this->_data)) {
+        if (null === $this->_data) {
             $this->refresh();
         }
 
@@ -135,7 +135,7 @@ public function getIndicesWithAlias($alias)
      */
     public function getResponse()
     {
-        if (\is_null($this->_response)) {
+        if (null === $this->_response) {
             $this->refresh();
         }
 
@@ -157,7 +157,7 @@ public function getShards()
     /**
      * Refresh status object.
      */
-    public function refresh()
+    public function refresh(): void
     {
         $this->_response = $this->_client->requestEndpoint(new Stats());
         $this->_data = $this->getResponse()->getData();
diff --git a/src/Suggest.php b/src/Suggest.php
index e10bc664cf..d7576b60f7 100644
--- a/src/Suggest.php
+++ b/src/Suggest.php
@@ -39,7 +39,7 @@ public function addSuggestion(AbstractSuggest $suggestion): self
     }
 
     /**
-     * @param Suggest|AbstractSuggest $suggestion
+     * @param AbstractSuggest|Suggest $suggestion
      *
      * @throws Exception\NotImplementedException
      */
diff --git a/src/Suggest/Term.php b/src/Suggest/Term.php
index 7aa27362cc..0d4b6763d6 100644
--- a/src/Suggest/Term.php
+++ b/src/Suggest/Term.php
@@ -103,7 +103,7 @@ public function setMaxInspections(int $max = 5): Term
     /**
      * Set the minimum number of documents in which a suggestion should appear.
      *
-     * @param int|float $min Defaults to 0. If the value is greater than 1, it must be a whole number.
+     * @param float|int $min Defaults to 0. If the value is greater than 1, it must be a whole number.
      *
      * @return $this
      */
diff --git a/src/Task.php b/src/Task.php
index a4cd2d2b23..3899847bc5 100644
--- a/src/Task.php
+++ b/src/Task.php
@@ -64,7 +64,7 @@ public function getId()
      */
     public function getData(): array
     {
-        if (\is_null($this->_data)) {
+        if (null === $this->_data) {
             $this->refresh();
         }
 
@@ -78,7 +78,7 @@ public function getData(): array
      */
     public function getResponse(): Response
     {
-        if (\is_null($this->_response)) {
+        if (null === $this->_response) {
             $this->refresh();
         }
 
@@ -90,7 +90,7 @@ public function getResponse(): Response
      *
      * @param array $options Options for endpoint
      */
-    public function refresh(array $options = [])
+    public function refresh(array $options = []): void
     {
         $endpoint = new \Elasticsearch\Endpoints\Tasks\Get();
         $endpoint->setTaskId($this->_id);
diff --git a/src/Transport/AbstractTransport.php b/src/Transport/AbstractTransport.php
index f25ffc4d34..cb6b63199a 100644
--- a/src/Transport/AbstractTransport.php
+++ b/src/Transport/AbstractTransport.php
@@ -107,7 +107,7 @@ public static function create($transport, Connection $connection, array $params
             } else {
                 $transport = \ucfirst($transport);
             }
-            $classNames = ["Elastica\\Transport\\$transport", $transport];
+            $classNames = ["Elastica\\Transport\\{$transport}", $transport];
             foreach ($classNames as $className) {
                 if (\class_exists($className)) {
                     $transport = new $className();
diff --git a/src/Transport/AwsAuthV4.php b/src/Transport/AwsAuthV4.php
index 184ca54aca..b070a361c6 100755
--- a/src/Transport/AwsAuthV4.php
+++ b/src/Transport/AwsAuthV4.php
@@ -72,7 +72,7 @@ private function getCredentialProvider(): callable
         return CredentialProvider::defaultProvider();
     }
 
-    private function initializePortAndScheme()
+    private function initializePortAndScheme(): void
     {
         $connection = $this->getConnection();
         if (true === $this->isSslRequired($connection)) {
diff --git a/src/Transport/Guzzle.php b/src/Transport/Guzzle.php
index 327c161765..4b2c394a25 100755
--- a/src/Transport/Guzzle.php
+++ b/src/Transport/Guzzle.php
@@ -69,11 +69,11 @@ public function exec(Request $request, array $params): Response
         $proxy = $connection->getProxy();
 
         // See: https://github.com/facebook/hhvm/issues/4875
-        if (\is_null($proxy) && \defined('HHVM_VERSION')) {
+        if (null === $proxy && \defined('HHVM_VERSION')) {
             $proxy = \getenv('http_proxy') ?: null;
         }
 
-        if (!\is_null($proxy)) {
+        if (null !== $proxy) {
             $options['proxy'] = $proxy;
         }
 
@@ -137,7 +137,8 @@ protected function _createPsr7Request(Request $request, Connection $connection)
             }
 
             $req = $req->withBody(
-                Psr7\stream_for(\is_array($data)
+                Psr7\stream_for(
+                    \is_array($data)
                     ? JSON::stringify($data, JSON_UNESCAPED_UNICODE)
                     : $data
                 )
@@ -202,7 +203,7 @@ protected function _getActionPath(Request $request): string
         if (!empty($query)) {
             $action .= '?'.\http_build_query(
                 $this->sanityzeQueryStringBool($query)
-                );
+            );
         }
 
         return $action;
diff --git a/src/Transport/Http.php b/src/Transport/Http.php
index 126d99c334..32f2f58208 100644
--- a/src/Transport/Http.php
+++ b/src/Transport/Http.php
@@ -72,7 +72,7 @@ public function exec(Request $request, array $params): Response
         if (!empty($query)) {
             $baseUri .= '?'.\http_build_query(
                 $this->sanityzeQueryStringBool($query)
-                );
+            );
         }
 
         \curl_setopt($conn, CURLOPT_URL, $baseUri);
@@ -93,19 +93,19 @@ public function exec(Request $request, array $params): Response
         $proxy = $connection->getProxy();
 
         // See: https://github.com/facebook/hhvm/issues/4875
-        if (\is_null($proxy) && \defined('HHVM_VERSION')) {
+        if (null === $proxy && \defined('HHVM_VERSION')) {
             $proxy = \getenv('http_proxy') ?: null;
         }
 
-        if (!\is_null($proxy)) {
+        if (null !== $proxy) {
             \curl_setopt($conn, CURLOPT_PROXY, $proxy);
         }
 
         $username = $connection->getUsername();
         $password = $connection->getPassword();
-        if (!\is_null($username) && !\is_null($password)) {
+        if (null !== $username && null !== $password) {
             \curl_setopt($conn, CURLOPT_HTTPAUTH, CURLAUTH_ANY);
-            \curl_setopt($conn, CURLOPT_USERPWD, "$username:$password");
+            \curl_setopt($conn, CURLOPT_USERPWD, "{$username}:{$password}");
         }
 
         $this->_setupCurl($conn);
@@ -198,7 +198,7 @@ public function exec(Request $request, array $params): Response
      *
      * @param resource $curlConnection Curl connection
      */
-    protected function _setupCurl($curlConnection)
+    protected function _setupCurl($curlConnection): void
     {
         if ($this->getConnection()->hasConfig('curl')) {
             foreach ($this->getConnection()->getConfig('curl') as $key => $param) {
diff --git a/src/Transport/Https.php b/src/Transport/Https.php
index 996bb2153b..54b2397406 100644
--- a/src/Transport/Https.php
+++ b/src/Transport/Https.php
@@ -21,7 +21,7 @@ class Https extends Http
      *
      * @param resource $connection Curl connection resource
      */
-    protected function _setupCurl($connection)
+    protected function _setupCurl($connection): void
     {
         parent::_setupCurl($connection);
     }
diff --git a/src/Transport/NullTransport.php b/src/Transport/NullTransport.php
index ca8b35d5d1..1e231b2095 100644
--- a/src/Transport/NullTransport.php
+++ b/src/Transport/NullTransport.php
@@ -22,7 +22,7 @@ class NullTransport extends AbstractTransport
      *
      * @var Response Response
      */
-    protected $_response = null;
+    protected $_response;
 
     /**
      * Set response object the transport returns.
diff --git a/src/Util.php b/src/Util.php
index 5c9c8dcc94..5e3f68ed82 100644
--- a/src/Util.php
+++ b/src/Util.php
@@ -88,9 +88,8 @@ public static function replaceBooleanWordsAndEscapeTerm($term)
     {
         $result = $term;
         $result = self::replaceBooleanWords($result);
-        $result = self::escapeTerm($result);
 
-        return $result;
+        return self::escapeTerm($result);
     }
 
     /**
@@ -137,9 +136,8 @@ public static function escapeTerm($term)
     public static function replaceBooleanWords($term)
     {
         $replacementMap = [' AND ' => ' && ', ' OR ' => ' || ', ' NOT ' => ' !'];
-        $result = \strtr($term, $replacementMap);
 
-        return $result;
+        return \strtr($term, $replacementMap);
     }
 
     /**
@@ -188,9 +186,8 @@ public static function convertDate($date)
         } else {
             $timestamp = \strtotime($date);
         }
-        $string = \date('Y-m-d\TH:i:s\Z', $timestamp);
 
-        return $string;
+        return \date('Y-m-d\TH:i:s\Z', $timestamp);
     }
 
     /**
@@ -203,16 +200,16 @@ public static function convertDate($date)
     public static function convertDateTimeObject(\DateTime $dateTime, bool $includeTimezone = true)
     {
         $formatString = 'Y-m-d\TH:i:s'.(true === $includeTimezone ? 'P' : '\Z');
-        $string = $dateTime->format($formatString);
 
-        return $string;
+        return $dateTime->format($formatString);
     }
 
     /**
      * Tries to guess the name of the param, based on its class
      * Example: \Elastica\Query\MatchAll => match_all.
      *
-     * @param string|object Object or class name
+     * @param object|string Object or class name
+     * @param mixed $class
      *
      * @return string parameter name
      */
diff --git a/tests/Aggregation/AbstractSimpleAggregationTest.php b/tests/Aggregation/AbstractSimpleAggregationTest.php
index 329a1dcd93..17e7adebaf 100644
--- a/tests/Aggregation/AbstractSimpleAggregationTest.php
+++ b/tests/Aggregation/AbstractSimpleAggregationTest.php
@@ -5,9 +5,12 @@
 use Elastica\Aggregation\AbstractSimpleAggregation;
 use Elastica\Exception\InvalidException;
 
+/**
+ * @internal
+ */
 class AbstractSimpleAggregationTest extends BaseAggregationTest
 {
-    protected function setUp()
+    protected function setUp(): void
     {
         $this->aggregation = $this->getMockForAbstractClass(
             AbstractSimpleAggregation::class,
@@ -15,7 +18,7 @@ protected function setUp()
         );
     }
 
-    public function testToArrayThrowsExceptionOnUnsetParams()
+    public function testToArrayThrowsExceptionOnUnsetParams(): void
     {
         $this->expectException(InvalidException::class);
         $this->expectExceptionMessage('Either the field param or the script param should be set');
diff --git a/tests/Aggregation/AdjacencyMatrixTest.php b/tests/Aggregation/AdjacencyMatrixTest.php
index 3fe9467449..d0eabc9fc6 100644
--- a/tests/Aggregation/AdjacencyMatrixTest.php
+++ b/tests/Aggregation/AdjacencyMatrixTest.php
@@ -10,26 +10,15 @@
 use Elastica\Query\Term;
 use Elastica\Query\Terms;
 
+/**
+ * @internal
+ */
 class AdjacencyMatrixTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-        $index->addDocuments([
-            new Document(1, ['accounts' => ['hillary', 'sidney']]),
-            new Document(2, ['accounts' => ['hillary', 'donald']]),
-            new Document(3, ['accounts' => ['vladimir', 'donald']]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $expected = [
             'adjacency_matrix' => [
@@ -70,7 +59,7 @@ public function testToArray()
     /**
      * @group unit
      */
-    public function testToArraySeparator()
+    public function testToArraySeparator(): void
     {
         $expected = [
             'adjacency_matrix' => [
@@ -95,7 +84,7 @@ public function testToArraySeparator()
     /**
      * @group functional
      */
-    public function testAdjacencyMatrixAggregation()
+    public function testAdjacencyMatrixAggregation(): void
     {
         $agg = new AdjacencyMatrix('interactions');
         $agg->addFilter(new Terms('accounts', ['hillary', 'sidney']), 'grpA');
@@ -134,4 +123,18 @@ public function testAdjacencyMatrixAggregation()
 
         $this->assertEquals($expected, $results['buckets']);
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+        $index->addDocuments([
+            new Document(1, ['accounts' => ['hillary', 'sidney']]),
+            new Document(2, ['accounts' => ['hillary', 'donald']]),
+            new Document(3, ['accounts' => ['vladimir', 'donald']]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/AggregationMetadataTest.php b/tests/Aggregation/AggregationMetadataTest.php
index 5b79d53a46..3dc0d904e1 100644
--- a/tests/Aggregation/AggregationMetadataTest.php
+++ b/tests/Aggregation/AggregationMetadataTest.php
@@ -5,20 +5,15 @@
 use Elastica\Aggregation\Cardinality;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class AggregationMetadataTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest()
-    {
-        $index = $this->_createIndex();
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group functional
      */
-    public function testAggregationSimpleMetadata()
+    public function testAggregationSimpleMetadata(): void
     {
         $aggName = 'mock';
         $metadata = ['color' => 'blue'];
@@ -37,7 +32,7 @@ public function testAggregationSimpleMetadata()
     /**
      * @group functional
      */
-    public function testAggregationComplexMetadata()
+    public function testAggregationComplexMetadata(): void
     {
         $aggName = 'mock';
         $metadata = [
@@ -59,4 +54,12 @@ public function testAggregationComplexMetadata()
 
         $this->assertEquals($metadata, $results['meta']);
     }
+
+    protected function _getIndexForTest()
+    {
+        $index = $this->_createIndex();
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/AvgBucketTest.php b/tests/Aggregation/AvgBucketTest.php
index 18f1990c5f..73a4140359 100644
--- a/tests/Aggregation/AvgBucketTest.php
+++ b/tests/Aggregation/AvgBucketTest.php
@@ -9,27 +9,15 @@
 use Elastica\Index;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class AvgBucketTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-
-        $index->addDocuments([
-            Document::create(['page' => 1, 'likes' => 180]),
-            Document::create(['page' => 1, 'likes' => 156]),
-            Document::create(['page' => 2, 'likes' => 155]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group functional
      */
-    public function testAvgBucketAggregation()
+    public function testAvgBucketAggregation(): void
     {
         $query = Query::create([])
             ->addAggregation(
@@ -44,7 +32,8 @@ public function testAvgBucketAggregation()
             ->addAggregation(
                 (new AvgBucket('avg_likes_by_page'))
                     ->setBucketsPath('pages>avg_likes')
-            );
+            )
+        ;
 
         $results = $this->_getIndexForTest()->search($query)->getAggregations();
 
@@ -56,14 +45,15 @@ public function testAvgBucketAggregation()
     /**
      * @group unit
      */
-    public function testConstructThroughSetters()
+    public function testConstructThroughSetters(): void
     {
         $serialDiffAgg = new AvgBucket('avg_bucket');
 
         $serialDiffAgg
             ->setBucketsPath('pages>avg_likes_by_page')
             ->setFormat('test_format')
-            ->setGapPolicy(10);
+            ->setGapPolicy(10)
+        ;
 
         $expected = [
             'avg_bucket' => [
@@ -79,11 +69,26 @@ public function testConstructThroughSetters()
     /**
      * @group unit
      */
-    public function testToArrayInvalidBucketsPath()
+    public function testToArrayInvalidBucketsPath(): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
 
         $serialDiffAgg = new AvgBucket('avg_bucket');
         $serialDiffAgg->toArray();
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+
+        $index->addDocuments([
+            Document::create(['page' => 1, 'likes' => 180]),
+            Document::create(['page' => 1, 'likes' => 156]),
+            Document::create(['page' => 2, 'likes' => 155]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/AvgTest.php b/tests/Aggregation/AvgTest.php
index fd48d1c794..65272532ab 100644
--- a/tests/Aggregation/AvgTest.php
+++ b/tests/Aggregation/AvgTest.php
@@ -7,28 +7,15 @@
 use Elastica\Index;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class AvgTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-
-        $index->addDocuments([
-            new Document(1, ['price' => 5]),
-            new Document(2, ['price' => 8]),
-            new Document(3, ['price' => 1]),
-            new Document(4, ['price' => 3]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group functional
      */
-    public function testAvgAggregation()
+    public function testAvgAggregation(): void
     {
         $agg = new Avg('avg');
         $agg->setField('price');
@@ -42,4 +29,20 @@ public function testAvgAggregation()
         $this->assertTrue($resultSet->hasAggregations());
         $this->assertEquals((5 + 8 + 1 + 3) / 4.0, $results['avg']['value']);
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+
+        $index->addDocuments([
+            new Document(1, ['price' => 5]),
+            new Document(2, ['price' => 8]),
+            new Document(3, ['price' => 1]),
+            new Document(4, ['price' => 3]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/BucketScriptTest.php b/tests/Aggregation/BucketScriptTest.php
index f5bf227ba9..241745c8a2 100644
--- a/tests/Aggregation/BucketScriptTest.php
+++ b/tests/Aggregation/BucketScriptTest.php
@@ -10,27 +10,15 @@
 use Elastica\Index;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class BucketScriptTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-
-        $index->addDocuments([
-            Document::create(['weight' => 60, 'height' => 180, 'age' => 25]),
-            Document::create(['weight' => 65, 'height' => 156, 'age' => 32]),
-            Document::create(['weight' => 50, 'height' => 155, 'age' => 45]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group functional
      */
-    public function testBucketScriptAggregation()
+    public function testBucketScriptAggregation(): void
     {
         $bucketScriptAggregation = new BucketScript(
             'result',
@@ -46,7 +34,8 @@ public function testBucketScriptAggregation()
         $histogramAggregation
             ->addAggregation((new Max('max_weight'))->setField('weight'))
             ->addAggregation((new Max('max_height'))->setField('height'))
-            ->addAggregation($bucketScriptAggregation);
+            ->addAggregation($bucketScriptAggregation)
+        ;
 
         $query = Query::create([])->addAggregation($histogramAggregation);
 
@@ -60,7 +49,7 @@ public function testBucketScriptAggregation()
     /**
      * @group unit
      */
-    public function testConstructThroughSetters()
+    public function testConstructThroughSetters(): void
     {
         $serialDiffAgg = new BucketScript('bucket_scripted');
 
@@ -72,7 +61,8 @@ public function testConstructThroughSetters()
                 'z' => 'agg_min',
             ])
             ->setFormat('test_format')
-            ->setGapPolicy(10);
+            ->setGapPolicy(10)
+        ;
 
         $expected = [
             'bucket_script' => [
@@ -93,7 +83,7 @@ public function testConstructThroughSetters()
     /**
      * @group unit
      */
-    public function testToArrayInvalidBucketsPath()
+    public function testToArrayInvalidBucketsPath(): void
     {
         $this->expectException(InvalidException::class);
 
@@ -104,11 +94,26 @@ public function testToArrayInvalidBucketsPath()
     /**
      * @group unit
      */
-    public function testToArrayInvalidScript()
+    public function testToArrayInvalidScript(): void
     {
         $this->expectException(InvalidException::class);
 
         $serialDiffAgg = new BucketScript('bucket_scripted', ['path' => 'agg']);
         $serialDiffAgg->toArray();
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+
+        $index->addDocuments([
+            Document::create(['weight' => 60, 'height' => 180, 'age' => 25]),
+            Document::create(['weight' => 65, 'height' => 156, 'age' => 32]),
+            Document::create(['weight' => 50, 'height' => 155, 'age' => 45]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/BucketSelectorTest.php b/tests/Aggregation/BucketSelectorTest.php
index 8bc9a0ef7a..57dc41c5c7 100644
--- a/tests/Aggregation/BucketSelectorTest.php
+++ b/tests/Aggregation/BucketSelectorTest.php
@@ -8,34 +8,15 @@
 use Elastica\Document;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class BucketSelectorTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest()
-    {
-        $index = $this->_createIndex();
-
-        $index->addDocuments([
-            new Document(1, ['date' => '2018-12-01', 'value' => 1]),
-            new Document(2, ['date' => '2018-12-02', 'value' => 2]),
-            new Document(3, ['date' => '2018-12-03', 'value' => 5]),
-            new Document(4, ['date' => '2018-12-04', 'value' => 4]),
-            new Document(5, ['date' => '2018-12-05', 'value' => 6]),
-            new Document(6, ['date' => '2018-12-06', 'value' => 9]),
-            new Document(7, ['date' => '2018-12-07', 'value' => 11]),
-            new Document(8, ['date' => '2018-12-08', 'value' => 4]),
-            new Document(9, ['date' => '2018-12-09', 'value' => 7]),
-            new Document(10, ['date' => '2018-12-10', 'value' => 4]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $expected = [
             'max' => [
@@ -63,7 +44,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testMaxAggregation()
+    public function testMaxAggregation(): void
     {
         $index = $this->_getIndexForTest();
 
@@ -88,4 +69,26 @@ public function testMaxAggregation()
         $this->assertEquals(11, $dateHistogramAggResult[2]['max_agg']['value']);
         $this->assertEquals(7, $dateHistogramAggResult[3]['max_agg']['value']);
     }
+
+    protected function _getIndexForTest()
+    {
+        $index = $this->_createIndex();
+
+        $index->addDocuments([
+            new Document(1, ['date' => '2018-12-01', 'value' => 1]),
+            new Document(2, ['date' => '2018-12-02', 'value' => 2]),
+            new Document(3, ['date' => '2018-12-03', 'value' => 5]),
+            new Document(4, ['date' => '2018-12-04', 'value' => 4]),
+            new Document(5, ['date' => '2018-12-05', 'value' => 6]),
+            new Document(6, ['date' => '2018-12-06', 'value' => 9]),
+            new Document(7, ['date' => '2018-12-07', 'value' => 11]),
+            new Document(8, ['date' => '2018-12-08', 'value' => 4]),
+            new Document(9, ['date' => '2018-12-09', 'value' => 7]),
+            new Document(10, ['date' => '2018-12-10', 'value' => 4]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/CardinalityTest.php b/tests/Aggregation/CardinalityTest.php
index 826195e370..f695f1638a 100644
--- a/tests/Aggregation/CardinalityTest.php
+++ b/tests/Aggregation/CardinalityTest.php
@@ -8,33 +8,15 @@
 use Elastica\Mapping;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class CardinalityTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-
-        $mapping = new Mapping([
-            'color' => ['type' => 'keyword'],
-        ]);
-        $index->setMapping($mapping);
-
-        $index->addDocuments([
-            new Document(1, ['color' => 'blue']),
-            new Document(2, ['color' => 'blue']),
-            new Document(3, ['color' => 'red']),
-            new Document(4, ['color' => 'green']),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group functional
      */
-    public function testCardinalityAggregation()
+    public function testCardinalityAggregation(): void
     {
         $agg = new Cardinality('cardinality');
         $agg->setField('color');
@@ -60,7 +42,7 @@ public function validPrecisionThresholdProvider()
      * @dataProvider validPrecisionThresholdProvider
      * @group unit
      */
-    public function testPrecisionThreshold(int $threshold)
+    public function testPrecisionThreshold(int $threshold): void
     {
         $agg = new Cardinality('threshold');
         $agg->setPrecisionThreshold($threshold);
@@ -75,7 +57,7 @@ public function testPrecisionThreshold(int $threshold)
      *
      * @param bool $rehash
      */
-    public function testRehash($rehash)
+    public function testRehash($rehash): void
     {
         $agg = new Cardinality('rehash');
         $agg->setRehash($rehash);
@@ -91,4 +73,25 @@ public function validRehashProvider()
             'false' => [false],
         ];
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+
+        $mapping = new Mapping([
+            'color' => ['type' => 'keyword'],
+        ]);
+        $index->setMapping($mapping);
+
+        $index->addDocuments([
+            new Document(1, ['color' => 'blue']),
+            new Document(2, ['color' => 'blue']),
+            new Document(3, ['color' => 'red']),
+            new Document(4, ['color' => 'green']),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/ChildrenTest.php b/tests/Aggregation/ChildrenTest.php
index 19196a2386..89ea47c226 100644
--- a/tests/Aggregation/ChildrenTest.php
+++ b/tests/Aggregation/ChildrenTest.php
@@ -8,8 +8,69 @@
 use Elastica\Mapping;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class ChildrenTest extends BaseAggregationTest
 {
+    /**
+     * @group functional
+     */
+    public function testChildrenAggregation(): void
+    {
+        $agg = new Children('answer');
+        $agg->setType('answer');
+
+        $names = new Terms('name');
+        $names->setField('name');
+
+        $agg->addAggregation($names);
+
+        $query = new Query();
+        $query->addAggregation($agg);
+
+        $index = $this->_getIndexForTest();
+        $aggregations = $index->search($query)->getAggregations();
+
+        // check children aggregation exists
+        $this->assertArrayHasKey('answer', $aggregations);
+
+        $childrenAggregations = $aggregations['answer'];
+
+        // check names aggregation exists inside children aggregation
+        $this->assertArrayHasKey('name', $childrenAggregations);
+    }
+
+    /**
+     * @group functional
+     */
+    public function testChildrenAggregationCount(): void
+    {
+        $agg = new Children('answer');
+        $agg->setType('answer');
+
+        $names = new Terms('name');
+        $names->setField('name');
+
+        $agg->addAggregation($names);
+
+        $query = new Query();
+        $query->addAggregation($agg);
+
+        $index = $this->_getIndexForTest();
+        $aggregations = $index->search($query)->getAggregations();
+
+        $childrenAggregations = $aggregations['answer'];
+        $this->assertCount(2, $childrenAggregations['name']['buckets']);
+
+        // check names aggregation works inside children aggregation
+        $names = [
+            ['key' => 'fede', 'doc_count' => 2],
+            ['key' => 'rico', 'doc_count' => 1],
+        ];
+        $this->assertEquals($names, $childrenAggregations['name']['buckets']);
+    }
+
     protected function _getIndexForTest(): Index
     {
         $client = $this->_getClient();
@@ -78,62 +139,4 @@ protected function _getIndexForTest(): Index
 
         return $index;
     }
-
-    /**
-     * @group functional
-     */
-    public function testChildrenAggregation()
-    {
-        $agg = new Children('answer');
-        $agg->setType('answer');
-
-        $names = new Terms('name');
-        $names->setField('name');
-
-        $agg->addAggregation($names);
-
-        $query = new Query();
-        $query->addAggregation($agg);
-
-        $index = $this->_getIndexForTest();
-        $aggregations = $index->search($query)->getAggregations();
-
-        // check children aggregation exists
-        $this->assertArrayHasKey('answer', $aggregations);
-
-        $childrenAggregations = $aggregations['answer'];
-
-        // check names aggregation exists inside children aggregation
-        $this->assertArrayHasKey('name', $childrenAggregations);
-    }
-
-    /**
-     * @group functional
-     */
-    public function testChildrenAggregationCount()
-    {
-        $agg = new Children('answer');
-        $agg->setType('answer');
-
-        $names = new Terms('name');
-        $names->setField('name');
-
-        $agg->addAggregation($names);
-
-        $query = new Query();
-        $query->addAggregation($agg);
-
-        $index = $this->_getIndexForTest();
-        $aggregations = $index->search($query)->getAggregations();
-
-        $childrenAggregations = $aggregations['answer'];
-        $this->assertCount(2, $childrenAggregations['name']['buckets']);
-
-        // check names aggregation works inside children aggregation
-        $names = [
-            ['key' => 'fede', 'doc_count' => 2],
-            ['key' => 'rico', 'doc_count' => 1],
-        ];
-        $this->assertEquals($names, $childrenAggregations['name']['buckets']);
-    }
 }
diff --git a/tests/Aggregation/DateHistogramTest.php b/tests/Aggregation/DateHistogramTest.php
index c16633fa15..b7b0c1fa68 100644
--- a/tests/Aggregation/DateHistogramTest.php
+++ b/tests/Aggregation/DateHistogramTest.php
@@ -8,30 +8,15 @@
 use Elastica\Mapping;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class DateHistogramTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-        $index->setMapping(new Mapping([
-            'created' => ['type' => 'date'],
-        ]));
-
-        $index->addDocuments([
-            new Document(1, ['created' => '2014-01-29T00:20:00']),
-            new Document(2, ['created' => '2014-01-29T02:20:00']),
-            new Document(3, ['created' => '2014-01-29T03:20:00']),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group functional
      */
-    public function testDateHistogramAggregation()
+    public function testDateHistogramAggregation(): void
     {
         $agg = new DateHistogram('hist', 'created', '1h');
 
@@ -57,7 +42,7 @@ public function testDateHistogramAggregation()
     /**
      * @group unit
      */
-    public function testSetOffset()
+    public function testSetOffset(): void
     {
         $agg = new DateHistogram('hist', 'created', '1h');
 
@@ -79,7 +64,7 @@ public function testSetOffset()
     /**
      * @group functional
      */
-    public function testSetOffsetWorks()
+    public function testSetOffsetWorks(): void
     {
         $this->_checkVersion('1.5');
 
@@ -96,7 +81,7 @@ public function testSetOffsetWorks()
     /**
      * @group unit
      */
-    public function testSetTimezone()
+    public function testSetTimezone(): void
     {
         $agg = new DateHistogram('hist', 'created', '1h');
 
@@ -114,4 +99,22 @@ public function testSetTimezone()
 
         $this->assertInstanceOf(DateHistogram::class, $agg->setTimezone('-02:30'));
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+        $index->setMapping(new Mapping([
+            'created' => ['type' => 'date'],
+        ]));
+
+        $index->addDocuments([
+            new Document(1, ['created' => '2014-01-29T00:20:00']),
+            new Document(2, ['created' => '2014-01-29T02:20:00']),
+            new Document(3, ['created' => '2014-01-29T03:20:00']),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/DateRangeTest.php b/tests/Aggregation/DateRangeTest.php
index 10b31c50cf..2e11e8b83f 100644
--- a/tests/Aggregation/DateRangeTest.php
+++ b/tests/Aggregation/DateRangeTest.php
@@ -9,30 +9,15 @@
 use Elastica\Mapping;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class DateRangeTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-        $index->setMapping(new Mapping([
-            'created' => ['type' => 'date', 'format' => 'epoch_millis'],
-        ]));
-
-        $index->addDocuments([
-            new Document(1, ['created' => 1390962135000]),
-            new Document(2, ['created' => 1390965735000]),
-            new Document(3, ['created' => 1390954935000]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group functional
      */
-    public function testDateRangeAggregation()
+    public function testDateRangeAggregation(): void
     {
         $agg = new DateRange('date');
         $agg->setField('created');
@@ -54,7 +39,7 @@ public function testDateRangeAggregation()
     /**
      * @group functional
      */
-    public function testDateRangeSetFormat()
+    public function testDateRangeSetFormat(): void
     {
         $agg = new DateRange('date');
         $agg->setField('created');
@@ -71,7 +56,7 @@ public function testDateRangeSetFormat()
     /**
      * @group functional
      */
-    public function testDateRangeSetFormatAccordingToFormatTargetField()
+    public function testDateRangeSetFormatAccordingToFormatTargetField(): void
     {
         $agg = new DateRange('date');
         $agg->setField('created');
@@ -91,4 +76,22 @@ public function testDateRangeSetFormatAccordingToFormatTargetField()
             $this->assertContains('failed to parse date field', $error['root_cause'][0]['reason']);
         }
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+        $index->setMapping(new Mapping([
+            'created' => ['type' => 'date', 'format' => 'epoch_millis'],
+        ]));
+
+        $index->addDocuments([
+            new Document(1, ['created' => 1390962135000]),
+            new Document(2, ['created' => 1390965735000]),
+            new Document(3, ['created' => 1390954935000]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/DerivativeTest.php b/tests/Aggregation/DerivativeTest.php
index 64c87e5fc8..3b451a2eec 100644
--- a/tests/Aggregation/DerivativeTest.php
+++ b/tests/Aggregation/DerivativeTest.php
@@ -8,29 +8,15 @@
 use Elastica\Document;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class DerivativeTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest()
-    {
-        $index = $this->_createIndex();
-
-        $index->addDocuments([
-            new Document(1, ['date' => '2018-12-01', 'value' => 1]),
-            new Document(2, ['date' => '2018-12-02', 'value' => 2]),
-            new Document(3, ['date' => '2018-12-03', 'value' => 2]),
-            new Document(4, ['date' => '2018-12-04', 'value' => 4]),
-            new Document(5, ['date' => '2018-12-05', 'value' => 3]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $expected = [
             'max' => [
@@ -57,7 +43,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testMaxAggregation()
+    public function testMaxAggregation(): void
     {
         $index = $this->_getIndexForTest();
 
@@ -82,4 +68,21 @@ public function testMaxAggregation()
         $this->assertEquals(2, $dateHistogramAggResult[3]['derivative_agg']['value']);
         $this->assertEquals(-1, $dateHistogramAggResult[4]['derivative_agg']['value']);
     }
+
+    protected function _getIndexForTest()
+    {
+        $index = $this->_createIndex();
+
+        $index->addDocuments([
+            new Document(1, ['date' => '2018-12-01', 'value' => 1]),
+            new Document(2, ['date' => '2018-12-02', 'value' => 2]),
+            new Document(3, ['date' => '2018-12-03', 'value' => 2]),
+            new Document(4, ['date' => '2018-12-04', 'value' => 4]),
+            new Document(5, ['date' => '2018-12-05', 'value' => 3]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/DiversifiedSamplerTest.php b/tests/Aggregation/DiversifiedSamplerTest.php
index a0c9f34674..35e5c5c834 100755
--- a/tests/Aggregation/DiversifiedSamplerTest.php
+++ b/tests/Aggregation/DiversifiedSamplerTest.php
@@ -9,43 +9,15 @@
 use Elastica\Mapping;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class DiversifiedSamplerTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex(null, true, 2);
-
-        $mapping = new Mapping([
-            'price' => ['type' => 'integer'],
-            'color' => ['type' => 'keyword'],
-        ]);
-        $index->setMapping($mapping);
-
-        $routing1 = 'first_routing';
-        $routing2 = 'second_routing';
-
-        $index->addDocuments([
-            (new Document(1, ['price' => 5, 'color' => 'blue']))->setRouting($routing1),
-            (new Document(2, ['price' => 8, 'color' => 'blue']))->setRouting($routing1),
-            (new Document(3, ['price' => 1, 'color' => 'blue']))->setRouting($routing1),
-            (new Document(4, ['price' => 3, 'color' => 'red']))->setRouting($routing1),
-            (new Document(5, ['price' => 1.5, 'color' => 'red']))->setRouting($routing1),
-            (new Document(6, ['price' => 2, 'color' => 'green']))->setRouting($routing1),
-            (new Document(7, ['price' => 5, 'color' => 'blue']))->setRouting($routing2),
-            (new Document(8, ['price' => 8, 'color' => 'blue']))->setRouting($routing2),
-            (new Document(9, ['price' => 1, 'color' => 'red']))->setRouting($routing2),
-            (new Document(10, ['price' => 3, 'color' => 'red']))->setRouting($routing2),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $expected = [
             'diversified_sampler' => [
@@ -82,7 +54,7 @@ public function testToArray()
      * @dataProvider shardSizeAndMaxDocPerValueProvider
      * @group functional
      */
-    public function testSamplerAggregation(int $shardSize, int $maxDocPerValue, int $docCount)
+    public function testSamplerAggregation(int $shardSize, int $maxDocPerValue, int $docCount): void
     {
         $agg = new DiversifiedSampler('price_diversified_sampler');
         $agg->setField('color');
@@ -117,4 +89,35 @@ public function shardSizeAndMaxDocPerValueProvider()
             [6, 2, 9],
         ];
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex(null, true, 2);
+
+        $mapping = new Mapping([
+            'price' => ['type' => 'integer'],
+            'color' => ['type' => 'keyword'],
+        ]);
+        $index->setMapping($mapping);
+
+        $routing1 = 'first_routing';
+        $routing2 = 'second_routing';
+
+        $index->addDocuments([
+            (new Document(1, ['price' => 5, 'color' => 'blue']))->setRouting($routing1),
+            (new Document(2, ['price' => 8, 'color' => 'blue']))->setRouting($routing1),
+            (new Document(3, ['price' => 1, 'color' => 'blue']))->setRouting($routing1),
+            (new Document(4, ['price' => 3, 'color' => 'red']))->setRouting($routing1),
+            (new Document(5, ['price' => 1.5, 'color' => 'red']))->setRouting($routing1),
+            (new Document(6, ['price' => 2, 'color' => 'green']))->setRouting($routing1),
+            (new Document(7, ['price' => 5, 'color' => 'blue']))->setRouting($routing2),
+            (new Document(8, ['price' => 8, 'color' => 'blue']))->setRouting($routing2),
+            (new Document(9, ['price' => 1, 'color' => 'red']))->setRouting($routing2),
+            (new Document(10, ['price' => 3, 'color' => 'red']))->setRouting($routing2),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/ExtendedStatsTest.php b/tests/Aggregation/ExtendedStatsTest.php
index 84a3f116c1..1f7cb3e719 100644
--- a/tests/Aggregation/ExtendedStatsTest.php
+++ b/tests/Aggregation/ExtendedStatsTest.php
@@ -7,28 +7,15 @@
 use Elastica\Index;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class ExtendedStatsTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-
-        $index->addDocuments([
-            new Document(1, ['price' => 5]),
-            new Document(2, ['price' => 8]),
-            new Document(3, ['price' => 1]),
-            new Document(4, ['price' => 3]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group functional
      */
-    public function testExtendedStatsAggregation()
+    public function testExtendedStatsAggregation(): void
     {
         $agg = new ExtendedStats('stats');
         $agg->setField('price');
@@ -44,4 +31,20 @@ public function testExtendedStatsAggregation()
         $this->assertEquals((5 + 8 + 1 + 3), $results['sum']);
         $this->assertArrayHasKey('sum_of_squares', $results);
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+
+        $index->addDocuments([
+            new Document(1, ['price' => 5]),
+            new Document(2, ['price' => 8]),
+            new Document(3, ['price' => 1]),
+            new Document(4, ['price' => 3]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/FilterTest.php b/tests/Aggregation/FilterTest.php
index 96aaae6417..eec6fe6cf5 100644
--- a/tests/Aggregation/FilterTest.php
+++ b/tests/Aggregation/FilterTest.php
@@ -10,28 +10,15 @@
 use Elastica\Query\Range;
 use Elastica\Query\Term;
 
+/**
+ * @internal
+ */
 class FilterTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-
-        $index->addDocuments([
-            new Document(1, ['price' => 5, 'color' => 'blue']),
-            new Document(2, ['price' => 8, 'color' => 'blue']),
-            new Document(3, ['price' => 1, 'color' => 'red']),
-            new Document(4, ['price' => 3, 'color' => 'green']),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $expected = [
             'filter' => ['range' => ['stock' => ['gt' => 0]]],
@@ -52,7 +39,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testFilterAggregation()
+    public function testFilterAggregation(): void
     {
         $agg = new Filter('filter');
         $agg->setFilter(new Term(['color' => 'blue']));
@@ -72,7 +59,7 @@ public function testFilterAggregation()
     /**
      * @group functional
      */
-    public function testFilterNoSubAggregation()
+    public function testFilterNoSubAggregation(): void
     {
         $agg = new Avg('price');
         $agg->setField('price');
@@ -89,7 +76,7 @@ public function testFilterNoSubAggregation()
     /**
      * @group unit
      */
-    public function testConstruct()
+    public function testConstruct(): void
     {
         $agg = new Filter('foo', new Term(['color' => 'blue']));
 
@@ -107,9 +94,25 @@ public function testConstruct()
     /**
      * @group unit
      */
-    public function testConstructWithoutFilter()
+    public function testConstructWithoutFilter(): void
     {
         $agg = new Filter('foo');
         $this->assertEquals('foo', $agg->getName());
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+
+        $index->addDocuments([
+            new Document(1, ['price' => 5, 'color' => 'blue']),
+            new Document(2, ['price' => 8, 'color' => 'blue']),
+            new Document(3, ['price' => 1, 'color' => 'red']),
+            new Document(4, ['price' => 3, 'color' => 'green']),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/FiltersTest.php b/tests/Aggregation/FiltersTest.php
index 663404469b..8ecd88c229 100644
--- a/tests/Aggregation/FiltersTest.php
+++ b/tests/Aggregation/FiltersTest.php
@@ -9,28 +9,15 @@
 use Elastica\Query;
 use Elastica\Query\Term;
 
+/**
+ * @internal
+ */
 class FiltersTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex('filter');
-
-        $index->addDocuments([
-            new Document(1, ['price' => 5, 'color' => 'blue']),
-            new Document(2, ['price' => 8, 'color' => 'blue']),
-            new Document(3, ['price' => 1, 'color' => 'red']),
-            new Document(4, ['price' => 3, 'color' => 'green']),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group unit
      */
-    public function testToArrayUsingNamedFilters()
+    public function testToArrayUsingNamedFilters(): void
     {
         $expected = [
             'filters' => [
@@ -71,7 +58,7 @@ public function testToArrayUsingNamedFilters()
     /**
      * @group unit
      */
-    public function testMixNamedAndAnonymousFilters()
+    public function testMixNamedAndAnonymousFilters(): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
         $this->expectExceptionMessage('Mix named and anonymous keys are not allowed');
@@ -84,7 +71,7 @@ public function testMixNamedAndAnonymousFilters()
     /**
      * @group unit
      */
-    public function testMixAnonymousAndNamedFilters()
+    public function testMixAnonymousAndNamedFilters(): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
         $this->expectExceptionMessage('Mix named and anonymous keys are not allowed');
@@ -98,7 +85,7 @@ public function testMixAnonymousAndNamedFilters()
     /**
      * @group unit
      */
-    public function testToArrayUsingAnonymousFilters()
+    public function testToArrayUsingAnonymousFilters(): void
     {
         $expected = [
             'filters' => [
@@ -131,7 +118,7 @@ public function testToArrayUsingAnonymousFilters()
     /**
      * @group unit
      */
-    public function testToArrayUsingOtherBucket()
+    public function testToArrayUsingOtherBucket(): void
     {
         $expected = [
             'filters' => [
@@ -158,7 +145,7 @@ public function testToArrayUsingOtherBucket()
     /**
      * @group functional
      */
-    public function testFilterAggregation()
+    public function testFilterAggregation(): void
     {
         $agg = new Filters('by_color');
         $agg->addFilter(new Term(['color' => 'blue']), 'blue');
@@ -186,7 +173,7 @@ public function testFilterAggregation()
     /**
      * @group functional
      */
-    public function testSetOtherBucket()
+    public function testSetOtherBucket(): void
     {
         $agg = new Filters('by_color');
         $agg->addFilter(new Term(['color' => 'red']), 'red');
@@ -214,7 +201,7 @@ public function testSetOtherBucket()
     /**
      * @group functional
      */
-    public function testSetOtherBucketKey()
+    public function testSetOtherBucketKey(): void
     {
         $agg = new Filters('by_color');
         $agg->addFilter(new Term(['color' => 'red']), 'red');
@@ -239,4 +226,20 @@ public function testSetOtherBucketKey()
         $this->assertEquals(1, $resultsForRed['avg_price']['value']);
         $this->assertEquals((5 + 8 + 3) / 3, $resultsForOtherBucket['avg_price']['value']);
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex('filter');
+
+        $index->addDocuments([
+            new Document(1, ['price' => 5, 'color' => 'blue']),
+            new Document(2, ['price' => 8, 'color' => 'blue']),
+            new Document(3, ['price' => 1, 'color' => 'red']),
+            new Document(4, ['price' => 3, 'color' => 'green']),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/GeoBoundsTest.php b/tests/Aggregation/GeoBoundsTest.php
index 9184b0903c..ecb16d9c6d 100644
--- a/tests/Aggregation/GeoBoundsTest.php
+++ b/tests/Aggregation/GeoBoundsTest.php
@@ -8,8 +8,28 @@
 use Elastica\Mapping;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class GeoBoundsTest extends BaseAggregationTest
 {
+    /**
+     * @group functional
+     */
+    public function testGeoBoundsAggregation(): void
+    {
+        $agg = new GeoBounds('viewport', 'location');
+
+        $query = new Query();
+        $query->addAggregation($agg);
+        $results = $this->getIndexForTest()->search($query)->getAggregation('viewport');
+
+        $this->assertEquals(37.782438984141, $results['bounds']['top_left']['lat']);
+        $this->assertEquals(-122.39256000146, $results['bounds']['top_left']['lon']);
+        $this->assertEquals(32.798319971189, $results['bounds']['bottom_right']['lat']);
+        $this->assertEquals(-117.24664804526, $results['bounds']['bottom_right']['lon']);
+    }
+
     private function getIndexForTest(): Index
     {
         $index = $this->_createIndex();
@@ -27,21 +47,4 @@ private function getIndexForTest(): Index
 
         return $index;
     }
-
-    /**
-     * @group functional
-     */
-    public function testGeoBoundsAggregation()
-    {
-        $agg = new GeoBounds('viewport', 'location');
-
-        $query = new Query();
-        $query->addAggregation($agg);
-        $results = $this->getIndexForTest()->search($query)->getAggregation('viewport');
-
-        $this->assertEquals(37.782438984141, $results['bounds']['top_left']['lat']);
-        $this->assertEquals(-122.39256000146, $results['bounds']['top_left']['lon']);
-        $this->assertEquals(32.798319971189, $results['bounds']['bottom_right']['lat']);
-        $this->assertEquals(-117.24664804526, $results['bounds']['bottom_right']['lon']);
-    }
 }
diff --git a/tests/Aggregation/GeoCentroidTest.php b/tests/Aggregation/GeoCentroidTest.php
index eabd678e62..b7220c9bc1 100644
--- a/tests/Aggregation/GeoCentroidTest.php
+++ b/tests/Aggregation/GeoCentroidTest.php
@@ -8,8 +8,25 @@
 use Elastica\Mapping;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class GeoCentroidTest extends BaseAggregationTest
 {
+    /**
+     * @group functional
+     */
+    public function testGeohashGridAggregation(): void
+    {
+        $agg = new GeoCentroid('centroid', 'location');
+
+        $query = new Query();
+        $query->addAggregation($agg);
+        $results = $this->_getIndexForTest()->search($query)->getAggregation('centroid');
+
+        $this->assertEquals(3, $results['count']);
+    }
+
     protected function _getIndexForTest(): Index
     {
         $index = $this->_createIndex();
@@ -27,18 +44,4 @@ protected function _getIndexForTest(): Index
 
         return $index;
     }
-
-    /**
-     * @group functional
-     */
-    public function testGeohashGridAggregation()
-    {
-        $agg = new GeoCentroid('centroid', 'location');
-
-        $query = new Query();
-        $query->addAggregation($agg);
-        $results = $this->_getIndexForTest()->search($query)->getAggregation('centroid');
-
-        $this->assertEquals(3, $results['count']);
-    }
 }
diff --git a/tests/Aggregation/GeoDistanceTest.php b/tests/Aggregation/GeoDistanceTest.php
index f86b5e215f..82d84f4904 100644
--- a/tests/Aggregation/GeoDistanceTest.php
+++ b/tests/Aggregation/GeoDistanceTest.php
@@ -8,8 +8,27 @@
 use Elastica\Mapping;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class GeoDistanceTest extends BaseAggregationTest
 {
+    /**
+     * @group functional
+     */
+    public function testGeoDistanceAggregation(): void
+    {
+        $agg = new GeoDistance('geo', 'location', ['lat' => 32.804654, 'lon' => -117.242594]);
+        $agg->addRange(null, 100);
+        $agg->setUnit('mi');
+
+        $query = new Query();
+        $query->addAggregation($agg);
+        $results = $this->_getIndexForTest()->search($query)->getAggregation('geo');
+
+        $this->assertEquals(2, $results['buckets'][0]['doc_count']);
+    }
+
     protected function _getIndexForTest(): Index
     {
         $index = $this->_createIndex();
@@ -27,20 +46,4 @@ protected function _getIndexForTest(): Index
 
         return $index;
     }
-
-    /**
-     * @group functional
-     */
-    public function testGeoDistanceAggregation()
-    {
-        $agg = new GeoDistance('geo', 'location', ['lat' => 32.804654, 'lon' => -117.242594]);
-        $agg->addRange(null, 100);
-        $agg->setUnit('mi');
-
-        $query = new Query();
-        $query->addAggregation($agg);
-        $results = $this->_getIndexForTest()->search($query)->getAggregation('geo');
-
-        $this->assertEquals(2, $results['buckets'][0]['doc_count']);
-    }
 }
diff --git a/tests/Aggregation/GeohashGridTest.php b/tests/Aggregation/GeohashGridTest.php
index 756fa1b824..897686a22d 100644
--- a/tests/Aggregation/GeohashGridTest.php
+++ b/tests/Aggregation/GeohashGridTest.php
@@ -8,8 +8,27 @@
 use Elastica\Mapping;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class GeohashGridTest extends BaseAggregationTest
 {
+    /**
+     * @group functional
+     */
+    public function testGeohashGridAggregation(): void
+    {
+        $agg = new GeohashGrid('hash', 'location');
+        $agg->setPrecision(3);
+
+        $query = new Query();
+        $query->addAggregation($agg);
+        $results = $this->_getIndexForTest()->search($query)->getAggregation('hash');
+
+        $this->assertEquals(2, $results['buckets'][0]['doc_count']);
+        $this->assertEquals(1, $results['buckets'][1]['doc_count']);
+    }
+
     protected function _getIndexForTest(): Index
     {
         $index = $this->_createIndex();
@@ -27,20 +46,4 @@ protected function _getIndexForTest(): Index
 
         return $index;
     }
-
-    /**
-     * @group functional
-     */
-    public function testGeohashGridAggregation()
-    {
-        $agg = new GeohashGrid('hash', 'location');
-        $agg->setPrecision(3);
-
-        $query = new Query();
-        $query->addAggregation($agg);
-        $results = $this->_getIndexForTest()->search($query)->getAggregation('hash');
-
-        $this->assertEquals(2, $results['buckets'][0]['doc_count']);
-        $this->assertEquals(1, $results['buckets'][1]['doc_count']);
-    }
 }
diff --git a/tests/Aggregation/GlobalAggregationTest.php b/tests/Aggregation/GlobalAggregationTest.php
index e6027930f3..5d5f007947 100644
--- a/tests/Aggregation/GlobalAggregationTest.php
+++ b/tests/Aggregation/GlobalAggregationTest.php
@@ -5,12 +5,15 @@
 use Elastica\Aggregation\Avg;
 use Elastica\Aggregation\GlobalAggregation;
 
+/**
+ * @internal
+ */
 class GlobalAggregationTest extends BaseAggregationTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $expected = [
             'global' => new \stdClass(),
diff --git a/tests/Aggregation/HistogramTest.php b/tests/Aggregation/HistogramTest.php
index fc7b25e53d..e1cd66c584 100644
--- a/tests/Aggregation/HistogramTest.php
+++ b/tests/Aggregation/HistogramTest.php
@@ -7,8 +7,29 @@
 use Elastica\Index;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class HistogramTest extends BaseAggregationTest
 {
+    /**
+     * @group functional
+     */
+    public function testHistogramAggregation(): void
+    {
+        $agg = new Histogram('hist', 'price', 10);
+        $agg->setMinimumDocumentCount(0); // should return empty buckets
+
+        $query = new Query();
+        $query->addAggregation($agg);
+        $results = $this->_getIndexForTest()->search($query)->getAggregation('hist');
+
+        $buckets = $results['buckets'];
+        $this->assertCount(5, $buckets);
+        $this->assertEquals(30, $buckets[3]['key']);
+        $this->assertEquals(2, $buckets[3]['doc_count']);
+    }
+
     protected function _getIndexForTest(): Index
     {
         $index = $this->_createIndex();
@@ -28,22 +49,4 @@ protected function _getIndexForTest(): Index
 
         return $index;
     }
-
-    /**
-     * @group functional
-     */
-    public function testHistogramAggregation()
-    {
-        $agg = new Histogram('hist', 'price', 10);
-        $agg->setMinimumDocumentCount(0); // should return empty buckets
-
-        $query = new Query();
-        $query->addAggregation($agg);
-        $results = $this->_getIndexForTest()->search($query)->getAggregation('hist');
-
-        $buckets = $results['buckets'];
-        $this->assertCount(5, $buckets);
-        $this->assertEquals(30, $buckets[3]['key']);
-        $this->assertEquals(2, $buckets[3]['doc_count']);
-    }
 }
diff --git a/tests/Aggregation/IpRangeTest.php b/tests/Aggregation/IpRangeTest.php
index ddd4e80a33..abb25b485b 100644
--- a/tests/Aggregation/IpRangeTest.php
+++ b/tests/Aggregation/IpRangeTest.php
@@ -8,30 +8,15 @@
 use Elastica\Mapping;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class IpRangeTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-        $index->setMapping(new Mapping([
-            'address' => ['type' => 'ip'],
-        ]));
-
-        $index->addDocuments([
-            new Document(1, ['address' => '192.168.1.100']),
-            new Document(2, ['address' => '192.168.1.150']),
-            new Document(3, ['address' => '192.168.1.200']),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group functional
      */
-    public function testIpRangeAggregation()
+    public function testIpRangeAggregation(): void
     {
         $agg = new IpRange('ip', 'address');
         $agg->addRange('192.168.1.101');
@@ -54,4 +39,22 @@ public function testIpRangeAggregation()
             }
         }
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+        $index->setMapping(new Mapping([
+            'address' => ['type' => 'ip'],
+        ]));
+
+        $index->addDocuments([
+            new Document(1, ['address' => '192.168.1.100']),
+            new Document(2, ['address' => '192.168.1.150']),
+            new Document(3, ['address' => '192.168.1.200']),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/MaxTest.php b/tests/Aggregation/MaxTest.php
index df51ed8b89..40a68c1e21 100644
--- a/tests/Aggregation/MaxTest.php
+++ b/tests/Aggregation/MaxTest.php
@@ -8,30 +8,17 @@
 use Elastica\Query;
 use Elastica\Script\Script;
 
+/**
+ * @internal
+ */
 class MaxTest extends BaseAggregationTest
 {
     private const MAX_PRICE = 8;
 
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-
-        $index->addDocuments([
-            new Document(1, ['price' => 5]),
-            new Document(2, ['price' => self::MAX_PRICE]),
-            new Document(3, ['price' => 1]),
-            new Document(4, ['price' => 3]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $expected = [
             'max' => [
@@ -61,7 +48,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testMaxAggregation()
+    public function testMaxAggregation(): void
     {
         $index = $this->_getIndexForTest();
 
@@ -82,4 +69,20 @@ public function testMaxAggregation()
 
         $this->assertEquals(self::MAX_PRICE * 1.2, $results['value']);
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+
+        $index->addDocuments([
+            new Document(1, ['price' => 5]),
+            new Document(2, ['price' => self::MAX_PRICE]),
+            new Document(3, ['price' => 1]),
+            new Document(4, ['price' => 3]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/MinTest.php b/tests/Aggregation/MinTest.php
index 57fc9ec439..3cfa9d83e3 100644
--- a/tests/Aggregation/MinTest.php
+++ b/tests/Aggregation/MinTest.php
@@ -7,10 +7,28 @@
 use Elastica\Index;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class MinTest extends BaseAggregationTest
 {
     private const MIN_PRICE = 1;
 
+    /**
+     * @group functional
+     */
+    public function testMinAggregation(): void
+    {
+        $agg = new Min('min_price');
+        $agg->setField('price');
+
+        $query = new Query();
+        $query->addAggregation($agg);
+        $results = $this->_getIndexForTest()->search($query)->getAggregation('min_price');
+
+        $this->assertEquals(self::MIN_PRICE, $results['value']);
+    }
+
     protected function _getIndexForTest(): Index
     {
         $index = $this->_createIndex();
@@ -26,19 +44,4 @@ protected function _getIndexForTest(): Index
 
         return $index;
     }
-
-    /**
-     * @group functional
-     */
-    public function testMinAggregation()
-    {
-        $agg = new Min('min_price');
-        $agg->setField('price');
-
-        $query = new Query();
-        $query->addAggregation($agg);
-        $results = $this->_getIndexForTest()->search($query)->getAggregation('min_price');
-
-        $this->assertEquals(self::MIN_PRICE, $results['value']);
-    }
 }
diff --git a/tests/Aggregation/MissingTest.php b/tests/Aggregation/MissingTest.php
index 2a4a151c13..a4abc5bccf 100644
--- a/tests/Aggregation/MissingTest.php
+++ b/tests/Aggregation/MissingTest.php
@@ -8,8 +8,25 @@
 use Elastica\Mapping;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class MissingTest extends BaseAggregationTest
 {
+    /**
+     * @group functional
+     */
+    public function testMissingAggregation(): void
+    {
+        $agg = new Missing('missing', 'color');
+
+        $query = new Query();
+        $query->addAggregation($agg);
+        $results = $this->_getIndexForTest()->search($query)->getAggregation('missing');
+
+        $this->assertEquals(1, $results['doc_count']);
+    }
+
     protected function _getIndexForTest(): Index
     {
         $index = $this->_createIndex();
@@ -30,18 +47,4 @@ protected function _getIndexForTest(): Index
 
         return $index;
     }
-
-    /**
-     * @group functional
-     */
-    public function testMissingAggregation()
-    {
-        $agg = new Missing('missing', 'color');
-
-        $query = new Query();
-        $query->addAggregation($agg);
-        $results = $this->_getIndexForTest()->search($query)->getAggregation('missing');
-
-        $this->assertEquals(1, $results['doc_count']);
-    }
 }
diff --git a/tests/Aggregation/NestedTest.php b/tests/Aggregation/NestedTest.php
index 9f7ea47f7d..e069388f0e 100644
--- a/tests/Aggregation/NestedTest.php
+++ b/tests/Aggregation/NestedTest.php
@@ -9,8 +9,29 @@
 use Elastica\Mapping;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class NestedTest extends BaseAggregationTest
 {
+    /**
+     * @group functional
+     */
+    public function testNestedAggregation(): void
+    {
+        $agg = new Nested('resellers', 'resellers');
+        $min = new Min('min_price');
+        $min->setField('resellers.price');
+        $agg->addAggregation($min);
+
+        $query = new Query();
+        $query->addAggregation($agg);
+
+        $results = $this->_getIndexForTest()->search($query)->getAggregation('resellers');
+
+        $this->assertEquals(4.98, $results['min_price']['value']);
+    }
+
     protected function _getIndexForTest(): Index
     {
         $index = $this->_createIndex();
@@ -44,22 +65,4 @@ protected function _getIndexForTest(): Index
 
         return $index;
     }
-
-    /**
-     * @group functional
-     */
-    public function testNestedAggregation()
-    {
-        $agg = new Nested('resellers', 'resellers');
-        $min = new Min('min_price');
-        $min->setField('resellers.price');
-        $agg->addAggregation($min);
-
-        $query = new Query();
-        $query->addAggregation($agg);
-
-        $results = $this->_getIndexForTest()->search($query)->getAggregation('resellers');
-
-        $this->assertEquals(4.98, $results['min_price']['value']);
-    }
 }
diff --git a/tests/Aggregation/ParentAggregationTest.php b/tests/Aggregation/ParentAggregationTest.php
index d47a1089c1..7ab73a1908 100644
--- a/tests/Aggregation/ParentAggregationTest.php
+++ b/tests/Aggregation/ParentAggregationTest.php
@@ -7,8 +7,85 @@
 use Elastica\Mapping;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class ParentAggregationTest extends BaseAggregationTest
 {
+    /**
+     * @group functional
+     */
+    public function testParentAggregation(): void
+    {
+        $agg = new ParentAggregation('question');
+        $agg->setType('answer');
+
+        $tags = new Terms('tags');
+        $tags->setField('tags');
+
+        $agg->addAggregation($tags);
+
+        $query = new Query();
+        $query->addAggregation($agg);
+
+        $index = $this->_getIndexForTest();
+        $aggregations = $index->search($query)->getAggregations();
+
+        // check parent aggregation exists
+        $this->assertArrayHasKey('question', $aggregations);
+
+        $parentAggregations = $aggregations['question'];
+
+        // check tags aggregation exists inside parent aggregation
+        $this->assertArrayHasKey('tags', $parentAggregations);
+    }
+
+    /**
+     * @group functional
+     */
+    public function testParentAggregationCount(): void
+    {
+        $topNames = new Terms('top-names');
+        $topNames->setField('owner')
+            ->setSize(10)
+        ;
+
+        $toQuestions = new ParentAggregation('to-questions');
+        $toQuestions->setType('answer');
+
+        $topTags = new Terms('top-tags');
+        $topTags->setField('tags')
+            ->setSize(10)
+        ;
+
+        $toQuestions->addAggregation($topTags);
+        $topNames->addAggregation($toQuestions);
+
+        $query = new Query();
+        $query->addAggregation($topNames);
+
+        $index = $this->_getIndexForTest();
+        $aggregations = $index->search($query)->getAggregations();
+
+        $topNamesAggregation = $aggregations['top-names'];
+        $this->assertCount(2, $topNamesAggregation['buckets']);
+        $this->assertEquals(2, $topNamesAggregation['buckets'][0]['to-questions']['doc_count']);
+        $this->assertEquals(1, $topNamesAggregation['buckets'][1]['to-questions']['doc_count']);
+
+        $samTags = [
+            ['key' => 'file-transfer', 'doc_count' => 2],
+            ['key' => 'windows-server-2008', 'doc_count' => 2],
+            ['key' => 'windows-server-2003', 'doc_count' => 1],
+        ];
+        $this->assertEquals($samTags, $topNamesAggregation['buckets'][0]['to-questions']['top-tags']['buckets']);
+
+        $samTags = [
+            ['key' => 'file-transfer', 'doc_count' => 1],
+            ['key' => 'windows-server-2008', 'doc_count' => 1],
+        ];
+        $this->assertEquals($samTags, $topNamesAggregation['buckets'][1]['to-questions']['top-tags']['buckets']);
+    }
+
     protected function _getIndexForTest()
     {
         $client = $this->_getClient();
@@ -88,76 +165,4 @@ protected function _getIndexForTest()
 
         return $index;
     }
-
-    /**
-     * @group functional
-     */
-    public function testParentAggregation()
-    {
-        $agg = new ParentAggregation('question');
-        $agg->setType('answer');
-
-        $tags = new Terms('tags');
-        $tags->setField('tags');
-
-        $agg->addAggregation($tags);
-
-        $query = new Query();
-        $query->addAggregation($agg);
-
-        $index = $this->_getIndexForTest();
-        $aggregations = $index->search($query)->getAggregations();
-
-        // check parent aggregation exists
-        $this->assertArrayHasKey('question', $aggregations);
-
-        $parentAggregations = $aggregations['question'];
-
-        // check tags aggregation exists inside parent aggregation
-        $this->assertArrayHasKey('tags', $parentAggregations);
-    }
-
-    /**
-     * @group functional
-     */
-    public function testParentAggregationCount()
-    {
-        $topNames = new Terms('top-names');
-        $topNames->setField('owner')
-                 ->setSize(10);
-
-        $toQuestions = new ParentAggregation('to-questions');
-        $toQuestions->setType('answer');
-
-        $topTags = new Terms('top-tags');
-        $topTags->setField('tags')
-                ->setSize(10);
-
-        $toQuestions->addAggregation($topTags);
-        $topNames->addAggregation($toQuestions);
-
-        $query = new Query();
-        $query->addAggregation($topNames);
-
-        $index = $this->_getIndexForTest();
-        $aggregations = $index->search($query)->getAggregations();
-
-        $topNamesAggregation = $aggregations['top-names'];
-        $this->assertCount(2, $topNamesAggregation['buckets']);
-        $this->assertEquals(2, $topNamesAggregation['buckets'][0]['to-questions']['doc_count']);
-        $this->assertEquals(1, $topNamesAggregation['buckets'][1]['to-questions']['doc_count']);
-
-        $samTags = [
-            ['key' => 'file-transfer', 'doc_count' => 2],
-            ['key' => 'windows-server-2008', 'doc_count' => 2],
-            ['key' => 'windows-server-2003', 'doc_count' => 1],
-        ];
-        $this->assertEquals($samTags, $topNamesAggregation['buckets'][0]['to-questions']['top-tags']['buckets']);
-
-        $samTags = [
-            ['key' => 'file-transfer', 'doc_count' => 1],
-            ['key' => 'windows-server-2008', 'doc_count' => 1],
-        ];
-        $this->assertEquals($samTags, $topNamesAggregation['buckets'][1]['to-questions']['top-tags']['buckets']);
-    }
 }
diff --git a/tests/Aggregation/PercentilesTest.php b/tests/Aggregation/PercentilesTest.php
index 4c1505cd13..c7114c4d03 100644
--- a/tests/Aggregation/PercentilesTest.php
+++ b/tests/Aggregation/PercentilesTest.php
@@ -6,12 +6,15 @@
 use Elastica\Document;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class PercentilesTest extends BaseAggregationTest
 {
     /**
      * @group functional
      */
-    public function testConstruct()
+    public function testConstruct(): void
     {
         $aggr = new Percentiles('price_percentile');
         $this->assertEquals('price_percentile', $aggr->getName());
@@ -23,7 +26,7 @@ public function testConstruct()
     /**
      * @group functional
      */
-    public function testSetField()
+    public function testSetField(): void
     {
         $aggr = new Percentiles('price_percentile');
         $aggr->setField('price');
@@ -35,7 +38,7 @@ public function testSetField()
     /**
      * @group unit
      */
-    public function testCompression()
+    public function testCompression(): void
     {
         $expected = [
             'percentiles' => [
@@ -57,7 +60,7 @@ public function testCompression()
     /**
      * @group unit
      */
-    public function testHdr()
+    public function testHdr(): void
     {
         $expected = [
             'percentiles' => [
@@ -79,7 +82,7 @@ public function testHdr()
     /**
      * @group functional
      */
-    public function testSetPercents()
+    public function testSetPercents(): void
     {
         $percents = [1, 2, 3];
         $aggr = new Percentiles('price_percentile');
@@ -91,7 +94,7 @@ public function testSetPercents()
     /**
      * @group functional
      */
-    public function testAddPercent()
+    public function testAddPercent(): void
     {
         $percents = [1, 2, 3];
         $aggr = new Percentiles('price_percentile');
@@ -106,7 +109,7 @@ public function testAddPercent()
     /**
      * @group functional
      */
-    public function testSetScript()
+    public function testSetScript(): void
     {
         $script = 'doc["load_time"].value / 20';
         $aggr = new Percentiles('price_percentile');
@@ -118,7 +121,7 @@ public function testSetScript()
     /**
      * @group functional
      */
-    public function testActualWork()
+    public function testActualWork(): void
     {
         // prepare
         $index = $this->_createIndex();
@@ -158,7 +161,7 @@ public function testActualWork()
     /**
      * @group functional
      */
-    public function testKeyed()
+    public function testKeyed(): void
     {
         $expected = [
             'values' => [
@@ -226,7 +229,7 @@ public function testKeyed()
     /**
      * @group unit
      */
-    public function testMissing()
+    public function testMissing(): void
     {
         $expected = [
             'percentiles' => [
diff --git a/tests/Aggregation/RangeTest.php b/tests/Aggregation/RangeTest.php
index 0caef375c8..a7b484a746 100644
--- a/tests/Aggregation/RangeTest.php
+++ b/tests/Aggregation/RangeTest.php
@@ -7,30 +7,15 @@
 use Elastica\Index;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class RangeTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-
-        $index->addDocuments([
-            new Document(1, ['price' => 5]),
-            new Document(2, ['price' => 8]),
-            new Document(3, ['price' => 1]),
-            new Document(4, ['price' => 3]),
-            new Document(5, ['price' => 1.5]),
-            new Document(6, ['price' => 2]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group functional
      */
-    public function testRangeAggregation()
+    public function testRangeAggregation(): void
     {
         $agg = new Range('range');
         $agg->setField('price');
@@ -46,7 +31,7 @@ public function testRangeAggregation()
     /**
      * @group unit
      */
-    public function testRangeAggregationWithKey()
+    public function testRangeAggregationWithKey(): void
     {
         $agg = new Range('range');
         $agg->setField('price');
@@ -77,4 +62,22 @@ public function testRangeAggregationWithKey()
 
         $this->assertEquals($expected, $agg->toArray());
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+
+        $index->addDocuments([
+            new Document(1, ['price' => 5]),
+            new Document(2, ['price' => 8]),
+            new Document(3, ['price' => 1]),
+            new Document(4, ['price' => 3]),
+            new Document(5, ['price' => 1.5]),
+            new Document(6, ['price' => 2]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/ReverseNestedTest.php b/tests/Aggregation/ReverseNestedTest.php
index 3a5c30f26d..693c11df2c 100644
--- a/tests/Aggregation/ReverseNestedTest.php
+++ b/tests/Aggregation/ReverseNestedTest.php
@@ -10,63 +10,15 @@
 use Elastica\Mapping;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class ReverseNestedTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-        $mapping = new Mapping();
-        $mapping->setProperties([
-            'comments' => [
-                'type' => 'nested',
-                'properties' => [
-                    'name' => ['type' => 'keyword'],
-                    'body' => ['type' => 'text'],
-                ],
-            ],
-            'tags' => ['type' => 'keyword'],
-        ]);
-
-        $index->setMapping($mapping);
-
-        $index->addDocuments([
-            new Document(1, [
-                'comments' => [
-                    [
-                        'name' => 'bob',
-                        'body' => 'this is bobs comment',
-                    ],
-                    [
-                        'name' => 'john',
-                        'body' => 'this is johns comment',
-                    ],
-                ],
-                'tags' => ['foo', 'bar'],
-            ]),
-            new Document(2, [
-                 'comments' => [
-                    [
-                        'name' => 'bob',
-                        'body' => 'this is another comment from bob',
-                    ],
-                    [
-                        'name' => 'susan',
-                        'body' => 'this is susans comment',
-                    ],
-                ],
-                'tags' => ['foo', 'baz'],
-            ]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group unit
      */
-    public function testPathNotSetIfNull()
+    public function testPathNotSetIfNull(): void
     {
         $agg = new ReverseNested('nested');
         $this->assertFalse($agg->hasParam('path'));
@@ -75,7 +27,7 @@ public function testPathNotSetIfNull()
     /**
      * @group unit
      */
-    public function testPathSetIfNotNull()
+    public function testPathSetIfNotNull(): void
     {
         $agg = new ReverseNested('nested', 'some_field');
         $this->assertEquals('some_field', $agg->getParam('path'));
@@ -84,7 +36,7 @@ public function testPathSetIfNotNull()
     /**
      * @group functional
      */
-    public function testReverseNestedAggregation()
+    public function testReverseNestedAggregation(): void
     {
         $agg = new Nested('comments', 'comments');
         $names = new Terms('name');
@@ -134,4 +86,55 @@ public function testReverseNestedAggregation()
         ];
         $this->assertEquals($tags, $nameResults['buckets'][2]['main']['tags']['buckets']);
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+        $mapping = new Mapping();
+        $mapping->setProperties([
+            'comments' => [
+                'type' => 'nested',
+                'properties' => [
+                    'name' => ['type' => 'keyword'],
+                    'body' => ['type' => 'text'],
+                ],
+            ],
+            'tags' => ['type' => 'keyword'],
+        ]);
+
+        $index->setMapping($mapping);
+
+        $index->addDocuments([
+            new Document(1, [
+                'comments' => [
+                    [
+                        'name' => 'bob',
+                        'body' => 'this is bobs comment',
+                    ],
+                    [
+                        'name' => 'john',
+                        'body' => 'this is johns comment',
+                    ],
+                ],
+                'tags' => ['foo', 'bar'],
+            ]),
+            new Document(2, [
+                'comments' => [
+                    [
+                        'name' => 'bob',
+                        'body' => 'this is another comment from bob',
+                    ],
+                    [
+                        'name' => 'susan',
+                        'body' => 'this is susans comment',
+                    ],
+                ],
+                'tags' => ['foo', 'baz'],
+            ]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/SamplerTest.php b/tests/Aggregation/SamplerTest.php
index 14b2d13c65..dc3bd01b46 100644
--- a/tests/Aggregation/SamplerTest.php
+++ b/tests/Aggregation/SamplerTest.php
@@ -8,32 +8,15 @@
 use Elastica\Index;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class SamplerTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex(null, true, 2);
-
-        $routing1 = 'first_routing';
-        $routing2 = 'second_routing';
-
-        $index->addDocuments([
-            (new Document(1, ['price' => 5]))->setRouting($routing1),
-            (new Document(2, ['price' => 8]))->setRouting($routing1),
-            (new Document(3, ['price' => 1]))->setRouting($routing1),
-            (new Document(4, ['price' => 3]))->setRouting($routing2),
-            (new Document(5, ['price' => 1.5]))->setRouting($routing2),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $expected = [
             'sampler' => [
@@ -63,7 +46,7 @@ public function testToArray()
      * @dataProvider shardSizeProvider
      * @group functional
      */
-    public function testSamplerAggregation(int $shardSize, int $docCount)
+    public function testSamplerAggregation(int $shardSize, int $docCount): void
     {
         $agg = new Sampler('price_sampler');
         $agg->setShardSize($shardSize);
@@ -88,4 +71,24 @@ public function shardSizeProvider()
             [3, 5],
         ];
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex(null, true, 2);
+
+        $routing1 = 'first_routing';
+        $routing2 = 'second_routing';
+
+        $index->addDocuments([
+            (new Document(1, ['price' => 5]))->setRouting($routing1),
+            (new Document(2, ['price' => 8]))->setRouting($routing1),
+            (new Document(3, ['price' => 1]))->setRouting($routing1),
+            (new Document(4, ['price' => 3]))->setRouting($routing2),
+            (new Document(5, ['price' => 1.5]))->setRouting($routing2),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/ScriptTest.php b/tests/Aggregation/ScriptTest.php
index 1fdf898481..0b0ad23ba8 100644
--- a/tests/Aggregation/ScriptTest.php
+++ b/tests/Aggregation/ScriptTest.php
@@ -8,28 +8,15 @@
 use Elastica\Query;
 use Elastica\Script\Script;
 
+/**
+ * @internal
+ */
 class ScriptTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-
-        $index->addDocuments([
-            new Document('1', ['price' => 5]),
-            new Document('2', ['price' => 8]),
-            new Document('3', ['price' => 1]),
-            new Document('4', ['price' => 3]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group functional
      */
-    public function testAggregationScript()
+    public function testAggregationScript(): void
     {
         $agg = new Sum('sum');
         $script = new Script("return doc['price'].value", null, Script::LANG_PAINLESS);
@@ -45,7 +32,7 @@ public function testAggregationScript()
     /**
      * @group functional
      */
-    public function testAggregationScriptAsString()
+    public function testAggregationScriptAsString(): void
     {
         $agg = new Sum('sum');
         $agg->setScript(new Script("doc['price'].value", null, Script::LANG_PAINLESS));
@@ -60,7 +47,7 @@ public function testAggregationScriptAsString()
     /**
      * @group unit
      */
-    public function testSetScript()
+    public function testSetScript(): void
     {
         $aggregation = 'sum';
         $string = "doc['price'].value";
@@ -87,4 +74,20 @@ public function testSetScript()
         ];
         $this->assertEquals($expected, $array);
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+
+        $index->addDocuments([
+            new Document('1', ['price' => 5]),
+            new Document('2', ['price' => 8]),
+            new Document('3', ['price' => 1]),
+            new Document('4', ['price' => 3]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/ScriptedMetricTest.php b/tests/Aggregation/ScriptedMetricTest.php
index b1a602a4dd..4152c02b14 100644
--- a/tests/Aggregation/ScriptedMetricTest.php
+++ b/tests/Aggregation/ScriptedMetricTest.php
@@ -8,32 +8,15 @@
 use Elastica\Mapping;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class ScriptedMetricTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-
-        $index->setMapping(new Mapping([
-            'start' => ['type' => 'long'],
-            'end' => ['type' => 'long'],
-        ]));
-
-        $index->addDocuments([
-            new Document(1, ['start' => 100, 'end' => 200]),
-            new Document(2, ['start' => 200, 'end' => 250]),
-            new Document(3, ['start' => 300, 'end' => 450]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group functional
      */
-    public function testScriptedMetricAggregation()
+    public function testScriptedMetricAggregation(): void
     {
         $agg = new ScriptedMetric(
             'scripted',
@@ -50,4 +33,24 @@ public function testScriptedMetricAggregation()
 
         $this->assertEquals([100, 50, 150], $results['value'][0]);
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+
+        $index->setMapping(new Mapping([
+            'start' => ['type' => 'long'],
+            'end' => ['type' => 'long'],
+        ]));
+
+        $index->addDocuments([
+            new Document(1, ['start' => 100, 'end' => 200]),
+            new Document(2, ['start' => 200, 'end' => 250]),
+            new Document(3, ['start' => 300, 'end' => 450]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/SerialDiffTest.php b/tests/Aggregation/SerialDiffTest.php
index 33c28d2cc2..cd29d5cbba 100644
--- a/tests/Aggregation/SerialDiffTest.php
+++ b/tests/Aggregation/SerialDiffTest.php
@@ -10,39 +10,22 @@
 use Elastica\Mapping;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class SerialDiffTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-
-        $index->setMapping(Mapping::create([
-            'value' => ['type' => 'long'],
-            'measured_at' => ['type' => 'date'],
-        ]));
-
-        $index->addDocuments([
-            Document::create(['value' => 100, 'measured_at' => '2016-08-23T15:00:00+0200']),
-            Document::create(['value' => 266, 'measured_at' => '2016-08-23T16:00:00+0200']),
-            Document::create(['value' => 350, 'measured_at' => '2016-08-23T17:00:00+0200']),
-            Document::create(['value' => 471, 'measured_at' => '2016-08-23T18:00:00+0200']),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group functional
      */
-    public function testSerialDiffAggregation()
+    public function testSerialDiffAggregation(): void
     {
         $dateHistogramAggregation = new DateHistogram('measurements', 'measured_at', 'hour');
 
         $dateHistogramAggregation
             ->addAggregation((new Max('max_value'))->setField('value'))
-            ->addAggregation(new SerialDiff('result', 'max_value'));
+            ->addAggregation(new SerialDiff('result', 'max_value'))
+        ;
 
         $query = Query::create([])->addAggregation($dateHistogramAggregation);
 
@@ -57,7 +40,7 @@ public function testSerialDiffAggregation()
     /**
      * @group unit
      */
-    public function testConstructThroughSetters()
+    public function testConstructThroughSetters(): void
     {
         $serialDiffAgg = new SerialDiff('difference');
 
@@ -65,7 +48,8 @@ public function testConstructThroughSetters()
             ->setBucketsPath('nested_agg')
             ->setFormat('test_format')
             ->setGapPolicy(10)
-            ->setLag(5);
+            ->setLag(5)
+        ;
 
         $expected = [
             'serial_diff' => [
@@ -82,11 +66,32 @@ public function testConstructThroughSetters()
     /**
      * @group unit
      */
-    public function testToArrayInvalidBucketsPath()
+    public function testToArrayInvalidBucketsPath(): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
 
         $serialDiffAgg = new SerialDiff('difference');
         $serialDiffAgg->toArray();
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+
+        $index->setMapping(Mapping::create([
+            'value' => ['type' => 'long'],
+            'measured_at' => ['type' => 'date'],
+        ]));
+
+        $index->addDocuments([
+            Document::create(['value' => 100, 'measured_at' => '2016-08-23T15:00:00+0200']),
+            Document::create(['value' => 266, 'measured_at' => '2016-08-23T16:00:00+0200']),
+            Document::create(['value' => 350, 'measured_at' => '2016-08-23T17:00:00+0200']),
+            Document::create(['value' => 471, 'measured_at' => '2016-08-23T18:00:00+0200']),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/SignificantTermsTest.php b/tests/Aggregation/SignificantTermsTest.php
index ce941310ed..cb9b19f598 100644
--- a/tests/Aggregation/SignificantTermsTest.php
+++ b/tests/Aggregation/SignificantTermsTest.php
@@ -9,34 +9,15 @@
 use Elastica\Query;
 use Elastica\Query\Terms;
 
+/**
+ * @internal
+ */
 class SignificantTermsTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-        $colors = ['blue', 'blue', 'red', 'red', 'green', 'yellow', 'white', 'cyan', 'magenta'];
-        $temperatures = [1500, 1500, 1500, 1500, 2500, 3500, 4500, 5500, 6500, 7500, 7500, 8500, 9500];
-
-        $mapping = new Mapping([
-            'color' => ['type' => 'keyword'],
-            'temperature' => ['type' => 'keyword'],
-        ]);
-        $index->setMapping($mapping);
-
-        $docs = [];
-        for ($i = 0; $i < 250; ++$i) {
-            $docs[] = new Document($i, ['color' => $colors[$i % \count($colors)], 'temperature' => $temperatures[$i % \count($temperatures)]]);
-        }
-        $index->addDocuments($docs);
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group functional
      */
-    public function testSignificantTermsAggregation()
+    public function testSignificantTermsAggregation(): void
     {
         $agg = new SignificantTerms('significantTerms');
         $agg->setField('temperature');
@@ -58,7 +39,7 @@ public function testSignificantTermsAggregation()
     /**
      * @group functional
      */
-    public function testSignificantTermsAggregationWithBackgroundFilter()
+    public function testSignificantTermsAggregationWithBackgroundFilter(): void
     {
         $agg = new SignificantTerms('significantTerms');
         $agg->setField('temperature');
@@ -82,7 +63,7 @@ public function testSignificantTermsAggregationWithBackgroundFilter()
     /**
      * @group functional
      */
-    public function testSignificantTermsAggregationWithBackgroundFilterWithLegacyFilter()
+    public function testSignificantTermsAggregationWithBackgroundFilterWithLegacyFilter(): void
     {
         $agg = new SignificantTerms('significantTerms');
         $agg->setField('temperature');
@@ -102,4 +83,26 @@ public function testSignificantTermsAggregationWithBackgroundFilterWithLegacyFil
         $this->assertEquals(12, $results['buckets'][0]['bg_count']);
         $this->assertEquals('4500', $results['buckets'][0]['key']);
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+        $colors = ['blue', 'blue', 'red', 'red', 'green', 'yellow', 'white', 'cyan', 'magenta'];
+        $temperatures = [1500, 1500, 1500, 1500, 2500, 3500, 4500, 5500, 6500, 7500, 7500, 8500, 9500];
+
+        $mapping = new Mapping([
+            'color' => ['type' => 'keyword'],
+            'temperature' => ['type' => 'keyword'],
+        ]);
+        $index->setMapping($mapping);
+
+        $docs = [];
+        for ($i = 0; $i < 250; ++$i) {
+            $docs[] = new Document($i, ['color' => $colors[$i % \count($colors)], 'temperature' => $temperatures[$i % \count($temperatures)]]);
+        }
+        $index->addDocuments($docs);
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/StatsBucketTest.php b/tests/Aggregation/StatsBucketTest.php
index 01458605e8..81cab3eee3 100644
--- a/tests/Aggregation/StatsBucketTest.php
+++ b/tests/Aggregation/StatsBucketTest.php
@@ -9,27 +9,15 @@
 use Elastica\Index;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class StatsBucketTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-
-        $index->addDocuments([
-            Document::create(['weight' => 60, 'height' => 180, 'age' => 25]),
-            Document::create(['weight' => 70, 'height' => 156, 'age' => 32]),
-            Document::create(['weight' => 50, 'height' => 155, 'age' => 45]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group functional
      */
-    public function testStatBucketAggregation()
+    public function testStatBucketAggregation(): void
     {
         $bucketScriptAggregation = new StatsBucket('result', 'age_groups>max_weight');
 
@@ -39,7 +27,8 @@ public function testStatBucketAggregation()
 
         $query = Query::create([])
             ->addAggregation($histogramAggregation)
-            ->addAggregation($bucketScriptAggregation);
+            ->addAggregation($bucketScriptAggregation)
+        ;
 
         $results = $this->_getIndexForTest()->search($query)->getAggregation('result');
 
@@ -53,14 +42,15 @@ public function testStatBucketAggregation()
     /**
      * @group unit
      */
-    public function testConstructThroughSetters()
+    public function testConstructThroughSetters(): void
     {
         $serialDiffAgg = new StatsBucket('bucket_part');
 
         $serialDiffAgg
             ->setBucketsPath('age_groups>max_weight')
             ->setFormat('test_format')
-            ->setGapPolicy(10);
+            ->setGapPolicy(10)
+        ;
 
         $expected = [
             'stats_bucket' => [
@@ -76,11 +66,26 @@ public function testConstructThroughSetters()
     /**
      * @group unit
      */
-    public function testToArrayInvalidBucketsPath()
+    public function testToArrayInvalidBucketsPath(): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
 
         $serialDiffAgg = new StatsBucket('bucket_part');
         $serialDiffAgg->toArray();
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+
+        $index->addDocuments([
+            Document::create(['weight' => 60, 'height' => 180, 'age' => 25]),
+            Document::create(['weight' => 70, 'height' => 156, 'age' => 32]),
+            Document::create(['weight' => 50, 'height' => 155, 'age' => 45]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/StatsTest.php b/tests/Aggregation/StatsTest.php
index 09492bf256..0aa2a5b1b5 100644
--- a/tests/Aggregation/StatsTest.php
+++ b/tests/Aggregation/StatsTest.php
@@ -7,28 +7,15 @@
 use Elastica\Index;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class StatsTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-
-        $index->addDocuments([
-            new Document(1, ['price' => 5]),
-            new Document(2, ['price' => 8]),
-            new Document(3, ['price' => 1]),
-            new Document(4, ['price' => 3]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group functional
      */
-    public function testStatsAggregation()
+    public function testStatsAggregation(): void
     {
         $agg = new Stats('stats');
         $agg->setField('price');
@@ -43,4 +30,20 @@ public function testStatsAggregation()
         $this->assertEquals((5 + 8 + 1 + 3) / 4.0, $results['avg']);
         $this->assertEquals((5 + 8 + 1 + 3), $results['sum']);
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+
+        $index->addDocuments([
+            new Document(1, ['price' => 5]),
+            new Document(2, ['price' => 8]),
+            new Document(3, ['price' => 1]),
+            new Document(4, ['price' => 3]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/SumBucketTest.php b/tests/Aggregation/SumBucketTest.php
index 552b8d3fd3..dc24c690a5 100644
--- a/tests/Aggregation/SumBucketTest.php
+++ b/tests/Aggregation/SumBucketTest.php
@@ -9,27 +9,15 @@
 use Elastica\Index;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class SumBucketTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-
-        $index->addDocuments([
-            Document::create(['page' => 1, 'likes' => 180]),
-            Document::create(['page' => 1, 'likes' => 156]),
-            Document::create(['page' => 2, 'likes' => 155]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group functional
      */
-    public function testSumBucketAggregation()
+    public function testSumBucketAggregation(): void
     {
         $query = Query::create([])
             ->addAggregation(
@@ -44,7 +32,8 @@ public function testSumBucketAggregation()
             ->addAggregation(
                 (new SumBucket('sum_likes_by_page'))
                     ->setBucketsPath('pages>sum_likes')
-            );
+            )
+        ;
 
         $results = $this->_getIndexForTest()->search($query)->getAggregations();
 
@@ -56,14 +45,15 @@ public function testSumBucketAggregation()
     /**
      * @group unit
      */
-    public function testConstructThroughSetters()
+    public function testConstructThroughSetters(): void
     {
         $serialDiffAgg = new SumBucket('sum_bucket');
 
         $serialDiffAgg
             ->setBucketsPath('pages>sum_likes_by_page')
             ->setFormat('test_format')
-            ->setGapPolicy(10);
+            ->setGapPolicy(10)
+        ;
 
         $expected = [
             'sum_bucket' => [
@@ -79,11 +69,26 @@ public function testConstructThroughSetters()
     /**
      * @group unit
      */
-    public function testToArrayInvalidBucketsPath()
+    public function testToArrayInvalidBucketsPath(): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
 
         $serialDiffAgg = new SumBucket('sum_bucket');
         $serialDiffAgg->toArray();
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+
+        $index->addDocuments([
+            Document::create(['page' => 1, 'likes' => 180]),
+            Document::create(['page' => 1, 'likes' => 156]),
+            Document::create(['page' => 2, 'likes' => 155]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/SumTest.php b/tests/Aggregation/SumTest.php
index a43a079e84..376e754a3a 100644
--- a/tests/Aggregation/SumTest.php
+++ b/tests/Aggregation/SumTest.php
@@ -7,8 +7,26 @@
 use Elastica\Index;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class SumTest extends BaseAggregationTest
 {
+    /**
+     * @group functional
+     */
+    public function testSumAggregation(): void
+    {
+        $agg = new Sum('sum');
+        $agg->setField('price');
+
+        $query = new Query();
+        $query->addAggregation($agg);
+        $results = $this->_getIndexForTest()->search($query)->getAggregation('sum');
+
+        $this->assertEquals(5 + 8 + 1 + 3, $results['value']);
+    }
+
     protected function _getIndexForTest(): Index
     {
         $index = $this->_createIndex();
@@ -24,19 +42,4 @@ protected function _getIndexForTest(): Index
 
         return $index;
     }
-
-    /**
-     * @group functional
-     */
-    public function testSumAggregation()
-    {
-        $agg = new Sum('sum');
-        $agg->setField('price');
-
-        $query = new Query();
-        $query->addAggregation($agg);
-        $results = $this->_getIndexForTest()->search($query)->getAggregation('sum');
-
-        $this->assertEquals(5 + 8 + 1 + 3, $results['value']);
-    }
 }
diff --git a/tests/Aggregation/TermsTest.php b/tests/Aggregation/TermsTest.php
index 7185a0a68f..87d8342391 100644
--- a/tests/Aggregation/TermsTest.php
+++ b/tests/Aggregation/TermsTest.php
@@ -8,33 +8,15 @@
 use Elastica\Mapping;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class TermsTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-
-        $mapping = new Mapping([
-            'color' => ['type' => 'keyword'],
-        ]);
-        $index->setMapping($mapping);
-
-        $index->addDocuments([
-            new Document(1, ['color' => 'blue']),
-            new Document(2, ['color' => 'blue']),
-            new Document(3, ['color' => 'red']),
-            new Document(4, ['color' => 'green']),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group functional
      */
-    public function testTermsAggregation()
+    public function testTermsAggregation(): void
     {
         $agg = new Terms('terms');
         $agg->setField('color');
@@ -50,7 +32,7 @@ public function testTermsAggregation()
     /**
      * @group functional
      */
-    public function testTermsSetOrder()
+    public function testTermsSetOrder(): void
     {
         $agg = new Terms('terms');
         $agg->setField('color');
@@ -66,7 +48,7 @@ public function testTermsSetOrder()
     /**
      * @group functional
      */
-    public function testTermsSetOrders()
+    public function testTermsSetOrders(): void
     {
         $agg = new Terms('terms');
         $agg->setField('color');
@@ -83,4 +65,25 @@ public function testTermsSetOrders()
         $this->assertSame('red', $results['buckets'][1]['key']);
         $this->assertSame('blue', $results['buckets'][2]['key']);
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+
+        $mapping = new Mapping([
+            'color' => ['type' => 'keyword'],
+        ]);
+        $index->setMapping($mapping);
+
+        $index->addDocuments([
+            new Document(1, ['color' => 'blue']),
+            new Document(2, ['color' => 'blue']),
+            new Document(3, ['color' => 'red']),
+            new Document(4, ['color' => 'green']),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Aggregation/TopHitsTest.php b/tests/Aggregation/TopHitsTest.php
index 410b5c3a2b..a6c76192c2 100644
--- a/tests/Aggregation/TopHitsTest.php
+++ b/tests/Aggregation/TopHitsTest.php
@@ -13,60 +13,15 @@
 use Elastica\Script\Script;
 use Elastica\Script\ScriptFields;
 
+/**
+ * @internal
+ */
 class TopHitsTest extends BaseAggregationTest
 {
-    protected function _getIndexForTest(): Index
-    {
-        $index = $this->_createIndex();
-        $mapping = new Mapping([
-            'tags' => ['type' => 'keyword'],
-            'title' => ['type' => 'keyword'],
-            'my_join_field' => [
-                'type' => 'join',
-                'relations' => [
-                    'question' => 'answer',
-                ],
-            ],
-        ]);
-        $index->setMapping($mapping);
-
-        $index->addDocuments([
-            new Document(1, [
-                'tags' => ['linux'],
-                'last_activity_date' => '2015-01-05',
-                'title' => 'Question about linux #1',
-            ]),
-            new Document(2, [
-                'tags' => ['linux'],
-                'last_activity_date' => '2014-12-23',
-                'title' => 'Question about linux #2',
-            ]),
-            new Document(3, [
-                'tags' => ['windows'],
-                'last_activity_date' => '2015-01-05',
-                'title' => 'Question about windows #1',
-            ]),
-            new Document(4, [
-                'tags' => ['windows'],
-                'last_activity_date' => '2014-12-23',
-                'title' => 'Question about windows #2',
-            ]),
-            new Document(5, [
-                'tags' => ['osx', 'apple'],
-                'last_activity_date' => '2014-12-23',
-                'title' => 'Question about osx',
-            ]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group unit
      */
-    public function testSetSize()
+    public function testSetSize(): void
     {
         $agg = new TopHits('agg_name');
         $returnValue = $agg->setSize(12);
@@ -77,7 +32,7 @@ public function testSetSize()
     /**
      * @group unit
      */
-    public function testSetFrom()
+    public function testSetFrom(): void
     {
         $agg = new TopHits('agg_name');
         $returnValue = $agg->setFrom(12);
@@ -88,7 +43,7 @@ public function testSetFrom()
     /**
      * @group unit
      */
-    public function testSetSort()
+    public function testSetSort(): void
     {
         $sort = ['last_activity_date' => ['order' => 'desc']];
         $agg = new TopHits('agg_name');
@@ -100,7 +55,7 @@ public function testSetSort()
     /**
      * @group unit
      */
-    public function testSetSource()
+    public function testSetSource(): void
     {
         $fields = ['title', 'tags'];
         $agg = new TopHits('agg_name');
@@ -112,7 +67,7 @@ public function testSetSource()
     /**
      * @group unit
      */
-    public function testSetVersion()
+    public function testSetVersion(): void
     {
         $agg = new TopHits('agg_name');
         $returnValue = $agg->setVersion(true);
@@ -126,7 +81,7 @@ public function testSetVersion()
     /**
      * @group unit
      */
-    public function testSetExplain()
+    public function testSetExplain(): void
     {
         $agg = new TopHits('agg_name');
         $returnValue = $agg->setExplain(true);
@@ -140,7 +95,7 @@ public function testSetExplain()
     /**
      * @group unit
      */
-    public function testSetHighlight()
+    public function testSetHighlight(): void
     {
         $highlight = [
             'fields' => [
@@ -156,7 +111,7 @@ public function testSetHighlight()
     /**
      * @group unit
      */
-    public function testSetFieldDataFields()
+    public function testSetFieldDataFields(): void
     {
         $fields = ['title', 'tags'];
         $agg = new TopHits('agg_name');
@@ -168,7 +123,7 @@ public function testSetFieldDataFields()
     /**
      * @group unit
      */
-    public function testSetScriptFields()
+    public function testSetScriptFields(): void
     {
         $script = new Script('1 + 2');
         $scriptFields = new ScriptFields(['three' => $script]);
@@ -182,7 +137,7 @@ public function testSetScriptFields()
     /**
      * @group unit
      */
-    public function testAddScriptField()
+    public function testAddScriptField(): void
     {
         $script = new Script('2+3');
         $agg = new TopHits('agg_name');
@@ -191,23 +146,10 @@ public function testAddScriptField()
         $this->assertInstanceOf(TopHits::class, $returnValue);
     }
 
-    protected function getOuterAggregationResult($innerAggr)
-    {
-        $outerAggr = new Terms('top_tags');
-        $outerAggr->setField('tags');
-        $outerAggr->setMinimumDocumentCount(2);
-        $outerAggr->addAggregation($innerAggr);
-
-        $query = new Query(new MatchAll());
-        $query->addAggregation($outerAggr);
-
-        return $this->_getIndexForTest()->search($query)->getAggregation('top_tags');
-    }
-
     /**
      * @group functional
      */
-    public function testAggregateUpdatedRecently()
+    public function testAggregateUpdatedRecently(): void
     {
         $aggr = new TopHits('top_tag_hits');
         $aggr->setSize(1);
@@ -226,7 +168,7 @@ public function testAggregateUpdatedRecently()
     /**
      * @group functional
      */
-    public function testAggregateUpdatedFarAgo()
+    public function testAggregateUpdatedFarAgo(): void
     {
         $aggr = new TopHits('top_tag_hits');
         $aggr->setSize(1);
@@ -245,7 +187,7 @@ public function testAggregateUpdatedFarAgo()
     /**
      * @group functional
      */
-    public function testAggregateTwoDocumentPerTag()
+    public function testAggregateTwoDocumentPerTag(): void
     {
         $aggr = new TopHits('top_tag_hits');
         $aggr->setSize(2);
@@ -263,7 +205,7 @@ public function testAggregateTwoDocumentPerTag()
     /**
      * @group functional
      */
-    public function testAggregateTwoDocumentPerTagWithOffset()
+    public function testAggregateTwoDocumentPerTagWithOffset(): void
     {
         $aggr = new TopHits('top_tag_hits');
         $aggr->setSize(2);
@@ -291,8 +233,10 @@ public function limitedSourceProvider()
     /**
      * @group functional
      * @dataProvider limitedSourceProvider
+     *
+     * @param mixed $source
      */
-    public function testAggregateWithLimitedSource($source)
+    public function testAggregateWithLimitedSource($source): void
     {
         $aggr = new TopHits('top_tag_hits');
         $aggr->setSource($source);
@@ -311,7 +255,7 @@ public function testAggregateWithLimitedSource($source)
     /**
      * @group functional
      */
-    public function testAggregateWithVersion()
+    public function testAggregateWithVersion(): void
     {
         $aggr = new TopHits('top_tag_hits');
         $aggr->setVersion(true);
@@ -328,7 +272,7 @@ public function testAggregateWithVersion()
     /**
      * @group functional
      */
-    public function testAggregateWithExplain()
+    public function testAggregateWithExplain(): void
     {
         $aggr = new TopHits('top_tag_hits');
         $aggr->setExplain(true);
@@ -345,7 +289,7 @@ public function testAggregateWithExplain()
     /**
      * @group functional
      */
-    public function testAggregateWithScriptFields()
+    public function testAggregateWithScriptFields(): void
     {
         $aggr = new TopHits('top_tag_hits');
         $aggr->setSize(1);
@@ -365,7 +309,7 @@ public function testAggregateWithScriptFields()
     /**
      * @group functional
      */
-    public function testAggregateWithHighlight()
+    public function testAggregateWithHighlight(): void
     {
         $queryString = new SimpleQueryString('linux', ['title']);
 
@@ -387,7 +331,7 @@ public function testAggregateWithHighlight()
     /**
      * @group functional
      */
-    public function testAggregateWithFieldData()
+    public function testAggregateWithFieldData(): void
     {
         $aggr = new TopHits('top_tag_hits');
         $aggr->setFieldDataFields(['title']);
@@ -405,4 +349,65 @@ public function testAggregateWithFieldData()
             $this->assertArrayNotHasKey('last_activity_date', $doc['fields']);
         }
     }
+
+    protected function _getIndexForTest(): Index
+    {
+        $index = $this->_createIndex();
+        $mapping = new Mapping([
+            'tags' => ['type' => 'keyword'],
+            'title' => ['type' => 'keyword'],
+            'my_join_field' => [
+                'type' => 'join',
+                'relations' => [
+                    'question' => 'answer',
+                ],
+            ],
+        ]);
+        $index->setMapping($mapping);
+
+        $index->addDocuments([
+            new Document(1, [
+                'tags' => ['linux'],
+                'last_activity_date' => '2015-01-05',
+                'title' => 'Question about linux #1',
+            ]),
+            new Document(2, [
+                'tags' => ['linux'],
+                'last_activity_date' => '2014-12-23',
+                'title' => 'Question about linux #2',
+            ]),
+            new Document(3, [
+                'tags' => ['windows'],
+                'last_activity_date' => '2015-01-05',
+                'title' => 'Question about windows #1',
+            ]),
+            new Document(4, [
+                'tags' => ['windows'],
+                'last_activity_date' => '2014-12-23',
+                'title' => 'Question about windows #2',
+            ]),
+            new Document(5, [
+                'tags' => ['osx', 'apple'],
+                'last_activity_date' => '2014-12-23',
+                'title' => 'Question about osx',
+            ]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
+
+    protected function getOuterAggregationResult($innerAggr)
+    {
+        $outerAggr = new Terms('top_tags');
+        $outerAggr->setField('tags');
+        $outerAggr->setMinimumDocumentCount(2);
+        $outerAggr->addAggregation($innerAggr);
+
+        $query = new Query(new MatchAll());
+        $query->addAggregation($outerAggr);
+
+        return $this->_getIndexForTest()->search($query)->getAggregation('top_tags');
+    }
 }
diff --git a/tests/Aggregation/ValueCountTest.php b/tests/Aggregation/ValueCountTest.php
index 1893f8dd49..9a51ada1a7 100644
--- a/tests/Aggregation/ValueCountTest.php
+++ b/tests/Aggregation/ValueCountTest.php
@@ -7,8 +7,25 @@
 use Elastica\Index;
 use Elastica\Query;
 
+/**
+ * @internal
+ */
 class ValueCountTest extends BaseAggregationTest
 {
+    /**
+     * @group functional
+     */
+    public function testValueCountAggregation(): void
+    {
+        $agg = new ValueCount('count', 'price');
+
+        $query = new Query();
+        $query->addAggregation($agg);
+        $results = $this->_getIndexForTest()->search($query)->getAggregation('count');
+
+        $this->assertEquals(5, $results['value']);
+    }
+
     protected function _getIndexForTest(): Index
     {
         $index = $this->_createIndex();
@@ -25,18 +42,4 @@ protected function _getIndexForTest(): Index
 
         return $index;
     }
-
-    /**
-     * @group functional
-     */
-    public function testValueCountAggregation()
-    {
-        $agg = new ValueCount('count', 'price');
-
-        $query = new Query();
-        $query->addAggregation($agg);
-        $results = $this->_getIndexForTest()->search($query)->getAggregation('count');
-
-        $this->assertEquals(5, $results['value']);
-    }
 }
diff --git a/tests/Base.php b/tests/Base.php
index f38a41456d..3ce2da766d 100644
--- a/tests/Base.php
+++ b/tests/Base.php
@@ -10,14 +10,36 @@
 use PHPUnit\Util\Test as TestUtil;
 use Psr\Log\LoggerInterface;
 
+/**
+ * @internal
+ */
 class Base extends TestCase
 {
-    protected static function hideDeprecated()
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        $hasGroup = $this->_isUnitGroup() || $this->_isFunctionalGroup() || $this->_isBenchmarkGroup();
+        $this->assertTrue($hasGroup, 'Every test must have one of "unit", "functional", "benchmark" group');
+        $this->showDeprecated();
+    }
+
+    protected function tearDown(): void
+    {
+        if ($this->_isFunctionalGroup()) {
+            $this->_getClient()->getIndex('_all')->delete();
+            $this->_getClient()->getIndex('_all')->clearCache();
+        }
+
+        parent::tearDown();
+    }
+
+    protected static function hideDeprecated(): void
     {
         \error_reporting(\error_reporting() & ~E_USER_DEPRECATED);
     }
 
-    protected static function showDeprecated()
+    protected static function showDeprecated(): void
     {
         \error_reporting(\error_reporting() | E_USER_DEPRECATED);
     }
@@ -84,7 +106,7 @@ protected static function buildUniqueId(): string
         return \preg_replace('/[^a-z]/i', '', \strtolower(static::class).\uniqid());
     }
 
-    protected function _createRenamePipeline()
+    protected function _createRenamePipeline(): void
     {
         $client = $this->_getClient();
 
@@ -105,7 +127,7 @@ protected function _createRenamePipeline()
         $client->requestEndpoint($endpoint);
     }
 
-    protected function _checkPlugin($plugin)
+    protected function _checkPlugin($plugin): void
     {
         $nodes = $this->_getClient()->getCluster()->getNodes();
         if (!$nodes[0]->getInfo()->hasPlugin($plugin)) {
@@ -120,7 +142,7 @@ protected function _getVersion()
         return \substr($data['version']['number'], 0, 1);
     }
 
-    protected function _checkVersion($version)
+    protected function _checkVersion($version): void
     {
         $data = $this->_getClient()->request('/')->getData();
         $installedVersion = $data['version']['number'];
@@ -130,7 +152,7 @@ protected function _checkVersion($version)
         }
     }
 
-    protected function _checkConnection($host, $port)
+    protected function _checkConnection($host, $port): void
     {
         $fp = @\pfsockopen($host, $port);
 
@@ -139,7 +161,7 @@ protected function _checkConnection($host, $port)
         }
     }
 
-    protected function _waitForAllocation(Index $index)
+    protected function _waitForAllocation(Index $index): void
     {
         do {
             $state = $index->getClient()->getCluster()->getState();
@@ -154,25 +176,6 @@ protected function _waitForAllocation(Index $index)
         } while (!$allocated);
     }
 
-    protected function setUp()
-    {
-        parent::setUp();
-
-        $hasGroup = $this->_isUnitGroup() || $this->_isFunctionalGroup() || $this->_isBenchmarkGroup();
-        $this->assertTrue($hasGroup, 'Every test must have one of "unit", "functional", "benchmark" group');
-        $this->showDeprecated();
-    }
-
-    protected function tearDown()
-    {
-        if ($this->_isFunctionalGroup()) {
-            $this->_getClient()->getIndex('_all')->delete();
-            $this->_getClient()->getIndex('_all')->clearCache();
-        }
-
-        parent::tearDown();
-    }
-
     protected function _isUnitGroup()
     {
         $groups = TestUtil::getGroups(\get_class($this), $this->getName(false));
diff --git a/tests/BasePipeline.php b/tests/BasePipeline.php
index 02ba77454f..beac80f36c 100644
--- a/tests/BasePipeline.php
+++ b/tests/BasePipeline.php
@@ -5,8 +5,17 @@
 use Elastica\Pipeline;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class BasePipeline extends BaseTest
 {
+    protected function tearDown(): void
+    {
+        $this->_createPipeline()->deletePipeline('*');
+        parent::tearDown();
+    }
+
     protected function _createPipeline(?string $id = null, string $description = ''): Pipeline
     {
         $id = $id ?: static::buildUniqueId();
@@ -17,10 +26,4 @@ protected function _createPipeline(?string $id = null, string $description = '')
 
         return $pipeline;
     }
-
-    protected function tearDown()
-    {
-        $this->_createPipeline()->deletePipeline('*');
-        parent::tearDown();
-    }
 }
diff --git a/tests/Bulk/Action/AbstractDocumentTest.php b/tests/Bulk/Action/AbstractDocumentTest.php
index f2e6bc45cc..d468f8ff0e 100644
--- a/tests/Bulk/Action/AbstractDocumentTest.php
+++ b/tests/Bulk/Action/AbstractDocumentTest.php
@@ -6,12 +6,15 @@
 use Elastica\Script\Script;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class AbstractDocumentTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testCreateAbstractDocumentWithInvalidParameter()
+    public function testCreateAbstractDocumentWithInvalidParameter(): void
     {
         $this->expectException(\InvalidArgumentException::class);
         $this->expectExceptionMessage('The data needs to be a Document or a Script.');
@@ -22,7 +25,7 @@ public function testCreateAbstractDocumentWithInvalidParameter()
     /**
      * @group unit
      */
-    public function testCreateAbstractDocumentWithScript()
+    public function testCreateAbstractDocumentWithScript(): void
     {
         $this->expectException(\InvalidArgumentException::class);
         $this->expectExceptionMessage('Scripts can only be used with the update operation type.');
diff --git a/tests/Bulk/Action/UpdateDocumentTest.php b/tests/Bulk/Action/UpdateDocumentTest.php
index 12c64ab42e..17a406d3c9 100644
--- a/tests/Bulk/Action/UpdateDocumentTest.php
+++ b/tests/Bulk/Action/UpdateDocumentTest.php
@@ -7,12 +7,15 @@
 use Elastica\Index;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class UpdateDocumentTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testUpdateDocument()
+    public function testUpdateDocument(): void
     {
         $document = new Document(null, ['foo' => 'bar']);
         $action = new UpdateDocument($document);
@@ -53,7 +56,7 @@ public function testUpdateDocument()
     /**
      * @group unit
      */
-    public function testUpdateDocumentAsUpsert()
+    public function testUpdateDocumentAsUpsert(): void
     {
         $document = new Document('1', ['foo' => 'bar'], 'index');
         $document->setDocAsUpsert(true);
diff --git a/tests/Bulk/ActionTest.php b/tests/Bulk/ActionTest.php
index def9518ac8..65e2b3a91e 100644
--- a/tests/Bulk/ActionTest.php
+++ b/tests/Bulk/ActionTest.php
@@ -6,12 +6,15 @@
 use Elastica\Index;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class ActionTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testAction()
+    public function testAction(): void
     {
         $action = new Action();
         $this->assertEquals('index', $action->getOpType());
diff --git a/tests/Bulk/ResponseSetTest.php b/tests/Bulk/ResponseSetTest.php
index f3b5398658..50631781d1 100644
--- a/tests/Bulk/ResponseSetTest.php
+++ b/tests/Bulk/ResponseSetTest.php
@@ -11,13 +11,16 @@
 use Elastica\Response;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class ResponseSetTest extends BaseTest
 {
     /**
      * @group unit
      * @dataProvider isOkDataProvider
      */
-    public function testIsOk(array $responseData, array $actions, bool $expected)
+    public function testIsOk(array $responseData, array $actions, bool $expected): void
     {
         $responseSet = $this->_createResponseSet($responseData, $actions);
         $this->assertEquals($expected, $responseSet->isOk());
@@ -26,7 +29,7 @@ public function testIsOk(array $responseData, array $actions, bool $expected)
     /**
      * @group unit
      */
-    public function testGetError()
+    public function testGetError(): void
     {
         list($responseData, $actions) = $this->_getFixture();
         $responseData['items'][1]['index']['ok'] = false;
@@ -64,7 +67,7 @@ public function testGetError()
     /**
      * @group unit
      */
-    public function testGetBulkResponses()
+    public function testGetBulkResponses(): void
     {
         list($responseData, $actions) = $this->_getFixture();
 
@@ -88,7 +91,7 @@ public function testGetBulkResponses()
     /**
      * @group unit
      */
-    public function testIterator()
+    public function testIterator(): void
     {
         list($responseData, $actions) = $this->_getFixture();
 
diff --git a/tests/BulkTest.php b/tests/BulkTest.php
index 38978c9828..7ec4c4298a 100644
--- a/tests/BulkTest.php
+++ b/tests/BulkTest.php
@@ -16,12 +16,15 @@
 use Elastica\Script\Script;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class BulkTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testSend()
+    public function testSend(): void
     {
         $index = $this->_createIndex();
         $indexName = $index->getName();
@@ -135,7 +138,7 @@ public function testSend()
     /**
      * @group functional
      */
-    public function testUnicodeBulkSend()
+    public function testUnicodeBulkSend(): void
     {
         $index = $this->_createIndex();
         $client = $index->getClient();
@@ -164,7 +167,7 @@ public function testUnicodeBulkSend()
     /**
      * @group functional
      */
-    public function testSetIndex()
+    public function testSetIndex(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('index');
@@ -191,7 +194,7 @@ public function testSetIndex()
     /**
      * @group unit
      */
-    public function testAddActions()
+    public function testAddActions(): void
     {
         $client = $this->_getClient();
         $bulk = new Bulk($client);
@@ -221,7 +224,7 @@ public function testAddActions()
     /**
      * @group unit
      */
-    public function testAddRawData()
+    public function testAddRawData(): void
     {
         $bulk = new Bulk($this->_getClient());
 
@@ -273,8 +276,11 @@ public function testAddRawData()
     /**
      * @group unit
      * @dataProvider invalidRawDataProvider
+     *
+     * @param mixed $rawData
+     * @param mixed $failMessage
      */
-    public function testInvalidRawData($rawData, $failMessage)
+    public function testInvalidRawData($rawData, $failMessage): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
 
@@ -328,7 +334,7 @@ public function invalidRawDataProvider()
     /**
      * @group functional
      */
-    public function testErrorRequest()
+    public function testErrorRequest(): void
     {
         $index = $this->_createIndex();
         $client = $index->getClient();
@@ -359,7 +365,7 @@ public function testErrorRequest()
     /**
      * @group functional
      */
-    public function testRawDocumentDataRequest()
+    public function testRawDocumentDataRequest(): void
     {
         $index = $this->_createIndex();
         $client = $index->getClient();
@@ -401,7 +407,7 @@ public function testRawDocumentDataRequest()
     /**
      * @group functional
      */
-    public function testUpdate()
+    public function testUpdate(): void
     {
         $index = $this->_createIndex();
         $client = $index->getClient();
@@ -535,7 +541,7 @@ public function testUpdate()
     /**
      * @group functional
      */
-    public function testUpsert()
+    public function testUpsert(): void
     {
         $index = $this->_createIndex();
         $client = $index->getClient();
@@ -583,7 +589,7 @@ public function testUpsert()
     /**
      * @group unit
      */
-    public function testGetPath()
+    public function testGetPath(): void
     {
         $client = $this->_getClient();
         $bulk = new Bulk($client);
@@ -599,7 +605,7 @@ public function testGetPath()
     /**
      * @group functional
      */
-    public function testRetry()
+    public function testRetry(): void
     {
         $index = $this->_createIndex();
         $client = $index->getClient();
@@ -631,7 +637,7 @@ public function testRetry()
     /**
      * @group unit
      */
-    public function testSetShardTimeout()
+    public function testSetShardTimeout(): void
     {
         $bulk = new Bulk($this->_getClient());
         $this->assertInstanceOf(Bulk::class, $bulk->setShardTimeout(10));
@@ -640,7 +646,7 @@ public function testSetShardTimeout()
     /**
      * @group unit
      */
-    public function testSetRequestParam()
+    public function testSetRequestParam(): void
     {
         $bulk = new Bulk($this->_getClient());
         $this->assertInstanceOf(Bulk::class, $bulk->setRequestParam('key', 'value'));
@@ -649,7 +655,7 @@ public function testSetRequestParam()
     /**
      * @group benchmark
      */
-    public function testMemoryUsage()
+    public function testMemoryUsage(): void
     {
         $index = $this->_createIndex();
 
@@ -682,7 +688,7 @@ public function testMemoryUsage()
     /**
      * @group unit
      */
-    public function testHasIndex()
+    public function testHasIndex(): void
     {
         $client = $this->_getClient();
         $bulk = new Bulk($client);
diff --git a/tests/ClientConfigurationTest.php b/tests/ClientConfigurationTest.php
index 4fc9754f3b..44d7459d9a 100644
--- a/tests/ClientConfigurationTest.php
+++ b/tests/ClientConfigurationTest.php
@@ -7,10 +7,12 @@
 
 /**
  * @group unit
+ *
+ * @internal
  */
 class ClientConfigurationTest extends TestCase
 {
-    public function testInvalidDsn()
+    public function testInvalidDsn(): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
         $this->expectExceptionMessage("DSN 'test:0' is invalid.");
@@ -18,7 +20,7 @@ public function testInvalidDsn()
         ClientConfiguration::fromDsn('test:0');
     }
 
-    public function testFromSimpleDsn()
+    public function testFromSimpleDsn(): void
     {
         $configuration = ClientConfiguration::fromDsn('192.168.1.1:9201');
 
@@ -42,7 +44,7 @@ public function testFromSimpleDsn()
         $this->assertEquals($expected, $configuration->getAll());
     }
 
-    public function testFromDsnWithParameters()
+    public function testFromDsnWithParameters(): void
     {
         $configuration = ClientConfiguration::fromDsn('https://user:p4ss@foo.com:9201/my-path?proxy=https://proxy.com&persistent=false&timeout=45&roundRobin=true&retryOnConflict=2&bigintConversion=true&extra=abc');
         $expected = [
@@ -66,7 +68,7 @@ public function testFromDsnWithParameters()
         $this->assertEquals($expected, $configuration->getAll());
     }
 
-    public function testFromEmptyArray()
+    public function testFromEmptyArray(): void
     {
         $configuration = ClientConfiguration::fromArray([]);
 
@@ -90,7 +92,7 @@ public function testFromEmptyArray()
         $this->assertEquals($expected, $configuration->getAll());
     }
 
-    public function testFromArray()
+    public function testFromArray(): void
     {
         $configuration = ClientConfiguration::fromArray([
             'username' => 'Jdoe',
@@ -118,14 +120,14 @@ public function testFromArray()
         $this->assertEquals($expected, $configuration->getAll());
     }
 
-    public function testHas()
+    public function testHas(): void
     {
         $configuration = new ClientConfiguration();
         $this->assertTrue($configuration->has('host'));
         $this->assertFalse($configuration->has('inexistantKey'));
     }
 
-    public function testGet()
+    public function testGet(): void
     {
         $configuration = new ClientConfiguration();
         $this->assertTrue($configuration->get('persistent'));
@@ -153,7 +155,7 @@ public function testGet()
         $configuration->get('invalidKey');
     }
 
-    public function testAdd()
+    public function testAdd(): void
     {
         $keyName = 'myKey';
 
diff --git a/tests/ClientFunctionalTest.php b/tests/ClientFunctionalTest.php
index 54df8caa61..136ce58ff2 100644
--- a/tests/ClientFunctionalTest.php
+++ b/tests/ClientFunctionalTest.php
@@ -22,6 +22,8 @@
 
 /**
  * @group functional
+ *
+ * @internal
  */
 class ClientFunctionalTest extends BaseTest
 {
@@ -63,17 +65,20 @@ public function testConnectionsArray(): void
         $index->create([], true);
 
         // Adds 1 document to the index
-        $doc1 = new Document(1,
+        $doc1 = new Document(
+            1,
             ['username' => 'hans', 'test' => ['2', '3', '5']]
         );
         $index->addDocument($doc1);
 
         // Adds a list of documents with _bulk upload to the index
         $docs = [];
-        $docs[] = new Document(2,
+        $docs[] = new Document(
+            2,
             ['username' => 'john', 'test' => ['1', '3', '6']]
         );
-        $docs[] = new Document(3,
+        $docs[] = new Document(
+            3,
             ['username' => 'rolf', 'test' => ['2', '3', '7']]
         );
         $index->addDocuments($docs);
@@ -95,17 +100,20 @@ public function testTwoServersSame(): void
         $index->create([], true);
 
         // Adds 1 document to the index
-        $doc1 = new Document(1,
+        $doc1 = new Document(
+            1,
             ['username' => 'hans', 'test' => ['2', '3', '5']]
         );
         $index->addDocument($doc1);
 
         // Adds a list of documents with _bulk upload to the index
         $docs = [];
-        $docs[] = new Document(2,
+        $docs[] = new Document(
+            2,
             ['username' => 'john', 'test' => ['1', '3', '6']]
         );
-        $docs[] = new Document(3,
+        $docs[] = new Document(
+            3,
             ['username' => 'rolf', 'test' => ['2', '3', '7']]
         );
         $index->addDocuments($docs);
@@ -376,7 +384,7 @@ public function testCallback(): void
         $count = 0;
 
         // Callback function which verifies that disabled connection objects are returned
-        $callback = function (Connection $connection, \Exception $exception, Client $client) use (&$count) {
+        $callback = function (Connection $connection, \Exception $exception, Client $client) use (&$count): void {
             $this->assertInstanceOf(Connection::class, $connection);
             $this->assertInstanceOf(ConnectionException::class, $exception);
             $this->assertInstanceOf(Client::class, $client);
@@ -853,7 +861,8 @@ public function testLogger(): void
                     $this->arrayHasKey('response'),
                     $this->arrayHasKey('responseStatus')
                 )
-            );
+            )
+        ;
 
         $client->request('_stats', Request::GET);
     }
@@ -878,7 +887,8 @@ public function testLoggerOnFailure(): void
                     $this->arrayHasKey('retry'),
                     $this->logicalNot($this->arrayHasKey('response'))
                 )
-            );
+            )
+        ;
 
         $client->request('_stats', Request::GET);
     }
@@ -949,6 +959,9 @@ public function testEndpointParamsRequest(): void
 
     /**
      * @dataProvider endpointQueryRequestDataProvider
+     *
+     * @param mixed $query
+     * @param mixed $totalHits
      */
     public function testEndpointQueryRequest($query, $totalHits): void
     {
diff --git a/tests/ClientTest.php b/tests/ClientTest.php
index c622e23618..41f6c1347f 100644
--- a/tests/ClientTest.php
+++ b/tests/ClientTest.php
@@ -9,6 +9,8 @@
 
 /**
  * @group unit
+ *
+ * @internal
  */
 class ClientTest extends BaseTest
 {
diff --git a/tests/Cluster/Health/IndexTest.php b/tests/Cluster/Health/IndexTest.php
index 779d45ebeb..092cd83157 100644
--- a/tests/Cluster/Health/IndexTest.php
+++ b/tests/Cluster/Health/IndexTest.php
@@ -6,6 +6,9 @@
 use Elastica\Cluster\Health\Shard;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class IndexTest extends BaseTest
 {
     /**
@@ -13,7 +16,7 @@ class IndexTest extends BaseTest
      */
     protected $_index;
 
-    protected function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
 
@@ -60,7 +63,7 @@ protected function setUp()
     /**
      * @group unit
      */
-    public function testGetName()
+    public function testGetName(): void
     {
         $this->assertEquals('test', $this->_index->getName());
     }
@@ -68,7 +71,7 @@ public function testGetName()
     /**
      * @group unit
      */
-    public function testGetStatus()
+    public function testGetStatus(): void
     {
         $this->assertEquals('yellow', $this->_index->getStatus());
     }
@@ -76,7 +79,7 @@ public function testGetStatus()
     /**
      * @group unit
      */
-    public function testGetNumberOfShards()
+    public function testGetNumberOfShards(): void
     {
         $this->assertEquals(1, $this->_index->getNumberOfShards());
     }
@@ -84,7 +87,7 @@ public function testGetNumberOfShards()
     /**
      * @group unit
      */
-    public function testGetNumberOfReplicas()
+    public function testGetNumberOfReplicas(): void
     {
         $this->assertEquals(2, $this->_index->getNumberOfReplicas());
     }
@@ -92,7 +95,7 @@ public function testGetNumberOfReplicas()
     /**
      * @group unit
      */
-    public function testGetActivePrimaryShards()
+    public function testGetActivePrimaryShards(): void
     {
         $this->assertEquals(3, $this->_index->getActivePrimaryShards());
     }
@@ -100,7 +103,7 @@ public function testGetActivePrimaryShards()
     /**
      * @group unit
      */
-    public function testGetActiveShards()
+    public function testGetActiveShards(): void
     {
         $this->assertEquals(4, $this->_index->getActiveShards());
     }
@@ -108,7 +111,7 @@ public function testGetActiveShards()
     /**
      * @group unit
      */
-    public function testGetRelocatingShards()
+    public function testGetRelocatingShards(): void
     {
         $this->assertEquals(5, $this->_index->getRelocatingShards());
     }
@@ -116,7 +119,7 @@ public function testGetRelocatingShards()
     /**
      * @group unit
      */
-    public function testGetInitializingShards()
+    public function testGetInitializingShards(): void
     {
         $this->assertEquals(6, $this->_index->getInitializingShards());
     }
@@ -124,7 +127,7 @@ public function testGetInitializingShards()
     /**
      * @group unit
      */
-    public function testGetUnassignedShards()
+    public function testGetUnassignedShards(): void
     {
         $this->assertEquals(7, $this->_index->getUnassignedShards());
     }
@@ -132,7 +135,7 @@ public function testGetUnassignedShards()
     /**
      * @group unit
      */
-    public function testGetShards()
+    public function testGetShards(): void
     {
         $shards = $this->_index->getShards();
 
diff --git a/tests/Cluster/Health/ShardTest.php b/tests/Cluster/Health/ShardTest.php
index 9f1b5cc877..26fc5ac400 100644
--- a/tests/Cluster/Health/ShardTest.php
+++ b/tests/Cluster/Health/ShardTest.php
@@ -5,6 +5,9 @@
 use Elastica\Cluster\Health\Shard;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class ShardTest extends BaseTest
 {
     /**
@@ -12,7 +15,7 @@ class ShardTest extends BaseTest
      */
     protected $_shard;
 
-    protected function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
 
@@ -31,7 +34,7 @@ protected function setUp()
     /**
      * @group unit
      */
-    public function testGetShardNumber()
+    public function testGetShardNumber(): void
     {
         $this->assertEquals(2, $this->_shard->getShardNumber());
     }
@@ -39,7 +42,7 @@ public function testGetShardNumber()
     /**
      * @group unit
      */
-    public function testGetStatus()
+    public function testGetStatus(): void
     {
         $this->assertEquals('red', $this->_shard->getStatus());
     }
@@ -47,7 +50,7 @@ public function testGetStatus()
     /**
      * @group unit
      */
-    public function testisPrimaryActive()
+    public function testisPrimaryActive(): void
     {
         $this->assertTrue($this->_shard->isPrimaryActive());
     }
@@ -55,7 +58,7 @@ public function testisPrimaryActive()
     /**
      * @group unit
      */
-    public function testIsActive()
+    public function testIsActive(): void
     {
         $this->assertTrue($this->_shard->isActive());
     }
@@ -63,7 +66,7 @@ public function testIsActive()
     /**
      * @group unit
      */
-    public function testIsRelocating()
+    public function testIsRelocating(): void
     {
         $this->assertFalse($this->_shard->isRelocating());
     }
@@ -71,7 +74,7 @@ public function testIsRelocating()
     /**
      * @group unit
      */
-    public function testIsInitialized()
+    public function testIsInitialized(): void
     {
         $this->assertFalse($this->_shard->isInitialized());
     }
@@ -79,7 +82,7 @@ public function testIsInitialized()
     /**
      * @group unit
      */
-    public function testIsUnassigned()
+    public function testIsUnassigned(): void
     {
         $this->assertTrue($this->_shard->isUnassigned());
     }
diff --git a/tests/Cluster/HealthTest.php b/tests/Cluster/HealthTest.php
index d87819ab47..b4346ceec5 100644
--- a/tests/Cluster/HealthTest.php
+++ b/tests/Cluster/HealthTest.php
@@ -6,6 +6,9 @@
 use Elastica\Cluster\Health\Index;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class HealthTest extends BaseTest
 {
     /**
@@ -13,7 +16,7 @@ class HealthTest extends BaseTest
      */
     protected $_health;
 
-    protected function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
 
@@ -46,12 +49,14 @@ protected function setUp()
             ->getMockBuilder(Health::class)
             ->setConstructorArgs([$this->_getClient()])
             ->setMethods(['_retrieveHealthData'])
-            ->getMock();
+            ->getMock()
+        ;
 
         $health
             ->expects($this->any())
             ->method('_retrieveHealthData')
-            ->will($this->returnValue($data));
+            ->will($this->returnValue($data))
+        ;
 
         // need to explicitly refresh because the mocking won't refresh the data in the constructor
         $health->refresh();
@@ -62,7 +67,7 @@ protected function setUp()
     /**
      * @group unit
      */
-    public function testGetClusterName()
+    public function testGetClusterName(): void
     {
         $this->assertEquals('test_cluster', $this->_health->getClusterName());
     }
@@ -70,7 +75,7 @@ public function testGetClusterName()
     /**
      * @group unit
      */
-    public function testGetStatus()
+    public function testGetStatus(): void
     {
         $this->assertEquals('green', $this->_health->getStatus());
     }
@@ -78,7 +83,7 @@ public function testGetStatus()
     /**
      * @group unit
      */
-    public function testGetTimedOut()
+    public function testGetTimedOut(): void
     {
         $this->assertFalse($this->_health->getTimedOut());
     }
@@ -86,7 +91,7 @@ public function testGetTimedOut()
     /**
      * @group unit
      */
-    public function testGetNumberOfNodes()
+    public function testGetNumberOfNodes(): void
     {
         $this->assertEquals(10, $this->_health->getNumberOfNodes());
     }
@@ -94,7 +99,7 @@ public function testGetNumberOfNodes()
     /**
      * @group unit
      */
-    public function testGetNumberOfDataNodes()
+    public function testGetNumberOfDataNodes(): void
     {
         $this->assertEquals(8, $this->_health->getNumberOfDataNodes());
     }
@@ -102,7 +107,7 @@ public function testGetNumberOfDataNodes()
     /**
      * @group unit
      */
-    public function testGetActivePrimaryShards()
+    public function testGetActivePrimaryShards(): void
     {
         $this->assertEquals(3, $this->_health->getActivePrimaryShards());
     }
@@ -110,7 +115,7 @@ public function testGetActivePrimaryShards()
     /**
      * @group unit
      */
-    public function testGetActiveShards()
+    public function testGetActiveShards(): void
     {
         $this->assertEquals(4, $this->_health->getActiveShards());
     }
@@ -118,7 +123,7 @@ public function testGetActiveShards()
     /**
      * @group unit
      */
-    public function testGetRelocatingShards()
+    public function testGetRelocatingShards(): void
     {
         $this->assertEquals(2, $this->_health->getRelocatingShards());
     }
@@ -126,7 +131,7 @@ public function testGetRelocatingShards()
     /**
      * @group unit
      */
-    public function testGetInitializingShards()
+    public function testGetInitializingShards(): void
     {
         $this->assertEquals(7, $this->_health->getInitializingShards());
     }
@@ -134,7 +139,7 @@ public function testGetInitializingShards()
     /**
      * @group unit
      */
-    public function testGetUnassignedShards()
+    public function testGetUnassignedShards(): void
     {
         $this->assertEquals(5, $this->_health->getUnassignedShards());
     }
@@ -142,7 +147,7 @@ public function testGetUnassignedShards()
     /**
      * @group unit
      */
-    public function testGetDelayedUnassignedShards()
+    public function testGetDelayedUnassignedShards(): void
     {
         $this->assertEquals(4, $this->_health->getDelayedUnassignedShards());
     }
@@ -150,7 +155,7 @@ public function testGetDelayedUnassignedShards()
     /**
      * @group unit
      */
-    public function testNumberOfPendingTasks()
+    public function testNumberOfPendingTasks(): void
     {
         $this->assertEquals(1, $this->_health->getNumberOfPendingTasks());
     }
@@ -158,7 +163,7 @@ public function testNumberOfPendingTasks()
     /**
      * @group unit
      */
-    public function testNumberOfInFlightFetch()
+    public function testNumberOfInFlightFetch(): void
     {
         $this->assertEquals(2, $this->_health->getNumberOfInFlightFetch());
     }
@@ -166,7 +171,7 @@ public function testNumberOfInFlightFetch()
     /**
      * @group unit
      */
-    public function testTaskMaxWaitingInQueueMillis()
+    public function testTaskMaxWaitingInQueueMillis(): void
     {
         $this->assertEquals(634, $this->_health->getTaskMaxWaitingInQueueMillis());
     }
@@ -174,7 +179,7 @@ public function testTaskMaxWaitingInQueueMillis()
     /**
      * @group unit
      */
-    public function testActiveShardsPercentAsNumber()
+    public function testActiveShardsPercentAsNumber(): void
     {
         $this->assertEquals(50, $this->_health->getActiveShardsPercentAsNumber());
     }
@@ -182,7 +187,7 @@ public function testActiveShardsPercentAsNumber()
     /**
      * @group unit
      */
-    public function testGetIndices()
+    public function testGetIndices(): void
     {
         $indices = $this->_health->getIndices();
 
diff --git a/tests/Cluster/SettingsTest.php b/tests/Cluster/SettingsTest.php
index eb39a8e9e3..d86cb03fde 100644
--- a/tests/Cluster/SettingsTest.php
+++ b/tests/Cluster/SettingsTest.php
@@ -7,12 +7,15 @@
 use Elastica\Exception\ResponseException;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class SettingsTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testSetTransient()
+    public function testSetTransient(): void
     {
         $index = $this->_createIndex();
 
@@ -34,7 +37,7 @@ public function testSetTransient()
     /**
      * @group functional
      */
-    public function testSetPersistent()
+    public function testSetPersistent(): void
     {
         $index = $this->_createIndex();
 
@@ -56,7 +59,7 @@ public function testSetPersistent()
     /**
      * @group functional
      */
-    public function testSetReadOnly()
+    public function testSetReadOnly(): void
     {
         // Create two indices to check that the complete cluster is read only
         $settings = new Settings($this->_getClient());
diff --git a/tests/ClusterTest.php b/tests/ClusterTest.php
index 6f8a7c0c57..66cdd528be 100644
--- a/tests/ClusterTest.php
+++ b/tests/ClusterTest.php
@@ -8,6 +8,8 @@
 
 /**
  * @group functional
+ *
+ * @internal
  */
 class ClusterTest extends BaseTest
 {
diff --git a/tests/Collapse/CollapseTest.php b/tests/Collapse/CollapseTest.php
index a7c94d0968..564cca1061 100644
--- a/tests/Collapse/CollapseTest.php
+++ b/tests/Collapse/CollapseTest.php
@@ -9,73 +9,15 @@
 use Elastica\Query;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class CollapseTest extends BaseTest
 {
-    private function _getIndexForCollapseTest()
-    {
-        $index = $this->_createIndex();
-        $index->setMapping(new Mapping([
-            'user' => ['type' => 'keyword'],
-            'message' => ['type' => 'text'],
-            'date' => ['type' => 'date'],
-            'likes' => ['type' => 'integer'],
-            'zip' => ['type' => 'keyword'],
-        ]));
-
-        $index->addDocuments([
-            new Document(1, [
-                'user' => 'Veronica',
-                'message' => 'Always keeping an eye on elasticsearch.',
-                'date' => '2019-08-15',
-                'likes' => 10,
-                'zip' => '07',
-            ]),
-            new Document(2, [
-                'user' => 'Wallace',
-                'message' => 'Elasticsearch DevOps is awesome!',
-                'date' => '2019-08-05',
-                'likes' => 50,
-                'zip' => '06',
-            ]),
-            new Document(3, [
-                'user' => 'Logan',
-                'message' => 'Can I find my lost stuff on elasticsearch?',
-                'date' => '2019-08-02',
-                'likes' => 1,
-                'zip' => '09',
-            ]),
-            new Document(4, [
-                'user' => 'Keith',
-                'message' => 'Investigating again.',
-                'date' => '2019-08-10',
-                'likes' => 30,
-                'zip' => '07',
-            ]),
-            new Document(5, [
-                'user' => 'Veronica',
-                'message' => 'Finding out new stuff.',
-                'date' => '2019-08-01',
-                'likes' => 20,
-                'zip' => '07',
-            ]),
-            new Document(6, [
-                'user' => 'Wallace',
-                'message' => 'Baller.',
-                'date' => '2019-08-15',
-                'likes' => 20,
-                'zip' => '06',
-            ]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group unit
      */
-    public function testSetFieldName()
+    public function testSetFieldName(): void
     {
         $collapse = new Collapse();
         $returnValue = $collapse->setFieldname('some_name');
@@ -86,7 +28,7 @@ public function testSetFieldName()
     /**
      * @group unit
      */
-    public function testSetInnerHits()
+    public function testSetInnerHits(): void
     {
         $collapse = new Collapse();
         $innerHits = new InnerHits();
@@ -99,7 +41,7 @@ public function testSetInnerHits()
     /**
      * @group unit
      */
-    public function testSetMaxConcurrentGroupSearches()
+    public function testSetMaxConcurrentGroupSearches(): void
     {
         $collapse = new Collapse();
         $returnValue = $collapse->setMaxConcurrentGroupSearches(5);
@@ -110,7 +52,7 @@ public function testSetMaxConcurrentGroupSearches()
     /**
      * @group unit
      */
-    public function testAddInnerHits()
+    public function testAddInnerHits(): void
     {
         $collapse = new Collapse();
 
@@ -132,7 +74,7 @@ public function testAddInnerHits()
     /**
      * @group unit
      */
-    public function testSetThenAddInnerHits()
+    public function testSetThenAddInnerHits(): void
     {
         $collapse = new Collapse();
 
@@ -154,7 +96,7 @@ public function testSetThenAddInnerHits()
     /**
      * @group unit
      */
-    public function testSetInnerHitsOverridesExistingValue()
+    public function testSetInnerHitsOverridesExistingValue(): void
     {
         $collapse = new Collapse();
 
@@ -184,7 +126,7 @@ public function testSetInnerHitsOverridesExistingValue()
     /**
      * @group functional
      */
-    public function testCollapseField()
+    public function testCollapseField(): void
     {
         $query = new Query();
         $query->setSource(false);
@@ -215,7 +157,7 @@ public function testCollapseField()
     /**
      * @group functional
      */
-    public function testCollapseWithInnerHits()
+    public function testCollapseWithInnerHits(): void
     {
         $query = new Query();
         $query->setSource(false);
@@ -238,16 +180,20 @@ public function testCollapseWithInnerHits()
         $this->assertEquals('1', $results->getResults()[0]->getId());
         $this->assertEquals('Veronica', $results->getResults()[0]->getData()['user'][0]);
         $this->assertEquals('2', $results->getResults()[0]->getInnerHits()['last_tweets']['hits']['total']['value']);
-        $this->assertEquals('Finding out new stuff.',
-            $results->getResults()[0]->getInnerHits()['last_tweets']['hits']['hits'][0]['_source']['message']);
-        $this->assertEquals('Always keeping an eye on elasticsearch.',
-            $results->getResults()[0]->getInnerHits()['last_tweets']['hits']['hits'][1]['_source']['message']);
+        $this->assertEquals(
+            'Finding out new stuff.',
+            $results->getResults()[0]->getInnerHits()['last_tweets']['hits']['hits'][0]['_source']['message']
+        );
+        $this->assertEquals(
+            'Always keeping an eye on elasticsearch.',
+            $results->getResults()[0]->getInnerHits()['last_tweets']['hits']['hits'][1]['_source']['message']
+        );
     }
 
     /**
      * @group functional
      */
-    public function testCollapseWithMultipleInnerHits()
+    public function testCollapseWithMultipleInnerHits(): void
     {
         $query = new Query();
         $query->setSource(false);
@@ -277,22 +223,30 @@ public function testCollapseWithMultipleInnerHits()
         $this->assertEquals('Veronica', $results->getResults()[0]->getData()['user'][0]);
 
         $this->assertEquals('2', $results->getResults()[0]->getInnerHits()['most_liked']['hits']['total']['value']);
-        $this->assertEquals('Always keeping an eye on elasticsearch.',
-            $results->getResults()[0]->getInnerHits()['most_liked']['hits']['hits'][0]['_source']['message']);
-        $this->assertEquals('Finding out new stuff.',
-            $results->getResults()[0]->getInnerHits()['most_liked']['hits']['hits'][1]['_source']['message']);
+        $this->assertEquals(
+            'Always keeping an eye on elasticsearch.',
+            $results->getResults()[0]->getInnerHits()['most_liked']['hits']['hits'][0]['_source']['message']
+        );
+        $this->assertEquals(
+            'Finding out new stuff.',
+            $results->getResults()[0]->getInnerHits()['most_liked']['hits']['hits'][1]['_source']['message']
+        );
 
         $this->assertEquals('2', $results->getResults()[0]->getInnerHits()['most_recent']['hits']['total']['value']);
-        $this->assertEquals('Finding out new stuff.',
-            $results->getResults()[0]->getInnerHits()['most_recent']['hits']['hits'][0]['_source']['message']);
-        $this->assertEquals('Always keeping an eye on elasticsearch.',
-            $results->getResults()[0]->getInnerHits()['most_recent']['hits']['hits'][1]['_source']['message']);
+        $this->assertEquals(
+            'Finding out new stuff.',
+            $results->getResults()[0]->getInnerHits()['most_recent']['hits']['hits'][0]['_source']['message']
+        );
+        $this->assertEquals(
+            'Always keeping an eye on elasticsearch.',
+            $results->getResults()[0]->getInnerHits()['most_recent']['hits']['hits'][1]['_source']['message']
+        );
     }
 
     /**
      * @group functional
      */
-    public function testSecondLevelCollapsing()
+    public function testSecondLevelCollapsing(): void
     {
         $query = new Query();
         $query->setSource(false);
@@ -323,6 +277,67 @@ public function testSecondLevelCollapsing()
         $this->assertEquals('Keith', $results->getResults()[0]->getInnerHits()['by_zip']['hits']['hits'][1]['fields']['user'][0]);
     }
 
+    private function _getIndexForCollapseTest()
+    {
+        $index = $this->_createIndex();
+        $index->setMapping(new Mapping([
+            'user' => ['type' => 'keyword'],
+            'message' => ['type' => 'text'],
+            'date' => ['type' => 'date'],
+            'likes' => ['type' => 'integer'],
+            'zip' => ['type' => 'keyword'],
+        ]));
+
+        $index->addDocuments([
+            new Document(1, [
+                'user' => 'Veronica',
+                'message' => 'Always keeping an eye on elasticsearch.',
+                'date' => '2019-08-15',
+                'likes' => 10,
+                'zip' => '07',
+            ]),
+            new Document(2, [
+                'user' => 'Wallace',
+                'message' => 'Elasticsearch DevOps is awesome!',
+                'date' => '2019-08-05',
+                'likes' => 50,
+                'zip' => '06',
+            ]),
+            new Document(3, [
+                'user' => 'Logan',
+                'message' => 'Can I find my lost stuff on elasticsearch?',
+                'date' => '2019-08-02',
+                'likes' => 1,
+                'zip' => '09',
+            ]),
+            new Document(4, [
+                'user' => 'Keith',
+                'message' => 'Investigating again.',
+                'date' => '2019-08-10',
+                'likes' => 30,
+                'zip' => '07',
+            ]),
+            new Document(5, [
+                'user' => 'Veronica',
+                'message' => 'Finding out new stuff.',
+                'date' => '2019-08-01',
+                'likes' => 20,
+                'zip' => '07',
+            ]),
+            new Document(6, [
+                'user' => 'Wallace',
+                'message' => 'Baller.',
+                'date' => '2019-08-15',
+                'likes' => 20,
+                'zip' => '06',
+            ]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
+
     /**
      * @return \Elastica\ResultSet
      */
diff --git a/tests/Connection/ConnectionPoolTest.php b/tests/Connection/ConnectionPoolTest.php
index 3cdbb18051..aa09b92bf6 100644
--- a/tests/Connection/ConnectionPoolTest.php
+++ b/tests/Connection/ConnectionPoolTest.php
@@ -9,13 +9,15 @@
 
 /**
  * @author chabior
+ *
+ * @internal
  */
 class ConnectionPoolTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testConstruct()
+    public function testConstruct(): void
     {
         $pool = $this->createPool();
 
@@ -25,7 +27,7 @@ public function testConstruct()
     /**
      * @group unit
      */
-    public function testSetConnections()
+    public function testSetConnections(): void
     {
         $pool = $this->createPool();
 
@@ -41,7 +43,7 @@ public function testSetConnections()
     /**
      * @group unit
      */
-    public function testAddConnection()
+    public function testAddConnection(): void
     {
         $pool = $this->createPool();
         $pool->setConnections([]);
@@ -60,7 +62,7 @@ public function testAddConnection()
     /**
      * @group unit
      */
-    public function testHasConnection()
+    public function testHasConnection(): void
     {
         $pool = $this->createPool();
 
@@ -70,7 +72,7 @@ public function testHasConnection()
     /**
      * @group unit
      */
-    public function testFailHasConnections()
+    public function testFailHasConnections(): void
     {
         $pool = $this->createPool();
 
diff --git a/tests/Connection/Strategy/CallbackStrategyTest.php b/tests/Connection/Strategy/CallbackStrategyTest.php
index ad50f608a9..ccac761777 100644
--- a/tests/Connection/Strategy/CallbackStrategyTest.php
+++ b/tests/Connection/Strategy/CallbackStrategyTest.php
@@ -10,13 +10,15 @@
  * Description of CallbackStrategyTest.
  *
  * @author chabior
+ *
+ * @internal
  */
 class CallbackStrategyTest extends Base
 {
     /**
      * @group unit
      */
-    public function testInvoke()
+    public function testInvoke(): void
     {
         $count = 0;
 
@@ -36,7 +38,7 @@ public function testInvoke()
     /**
      * @group functional
      */
-    public function testConnection()
+    public function testConnection(): void
     {
         $count = 0;
 
diff --git a/tests/Connection/Strategy/RoundRobinTest.php b/tests/Connection/Strategy/RoundRobinTest.php
index f9f8c788b0..b15d661ed0 100644
--- a/tests/Connection/Strategy/RoundRobinTest.php
+++ b/tests/Connection/Strategy/RoundRobinTest.php
@@ -13,6 +13,8 @@
  * Description of RoundRobinTest.
  *
  * @author chabior
+ *
+ * @internal
  */
 class RoundRobinTest extends Base
 {
@@ -24,7 +26,7 @@ class RoundRobinTest extends Base
     /**
      * @group functional
      */
-    public function testConnection()
+    public function testConnection(): void
     {
         $config = ['connectionStrategy' => 'RoundRobin'];
         $client = $this->_getClient($config);
@@ -39,7 +41,7 @@ public function testConnection()
     /**
      * @group unit
      */
-    public function testOldStrategySet()
+    public function testOldStrategySet(): void
     {
         $config = ['roundRobin' => true];
         $client = $this->_getClient($config);
@@ -50,7 +52,7 @@ public function testOldStrategySet()
     /**
      * @group functional
      */
-    public function testFailConnection()
+    public function testFailConnection(): void
     {
         $this->expectException(\Elastica\Exception\ConnectionException::class);
 
@@ -65,7 +67,7 @@ public function testFailConnection()
     /**
      * @group functional
      */
-    public function testWithOneFailConnection()
+    public function testWithOneFailConnection(): void
     {
         $connections = [
             new Connection(['host' => '255.255.255.0', 'timeout' => $this->_timeout]),
@@ -73,7 +75,7 @@ public function testWithOneFailConnection()
         ];
 
         $count = 0;
-        $callback = function ($connection, $exception, $client) use (&$count) {
+        $callback = function ($connection, $exception, $client) use (&$count): void {
             ++$count;
         };
 
@@ -93,7 +95,7 @@ public function testWithOneFailConnection()
     /**
      * @group functional
      */
-    public function testWithNoValidConnection()
+    public function testWithNoValidConnection(): void
     {
         $connections = [
             new Connection(['host' => '255.255.255.0', 'timeout' => $this->_timeout]),
@@ -102,7 +104,7 @@ public function testWithNoValidConnection()
         ];
 
         $count = 0;
-        $client = $this->_getClient(['roundRobin' => true], function () use (&$count) {
+        $client = $this->_getClient(['roundRobin' => true], function () use (&$count): void {
             ++$count;
         });
 
@@ -117,14 +119,14 @@ public function testWithNoValidConnection()
         }
     }
 
-    protected function _checkStrategy(Client $client)
+    protected function _checkStrategy(Client $client): void
     {
         $strategy = $client->getConnectionStrategy();
 
         $this->assertInstanceOf(RoundRobin::class, $strategy);
     }
 
-    protected function _checkResponse(Response $response)
+    protected function _checkResponse(Response $response): void
     {
         $this->assertTrue($response->isOk());
     }
diff --git a/tests/Connection/Strategy/SimpleTest.php b/tests/Connection/Strategy/SimpleTest.php
index a3a52fa2dd..40b5035daa 100644
--- a/tests/Connection/Strategy/SimpleTest.php
+++ b/tests/Connection/Strategy/SimpleTest.php
@@ -13,6 +13,8 @@
  * Description of SimplyTest.
  *
  * @author chabior
+ *
+ * @internal
  */
 class SimpleTest extends Base
 {
@@ -24,7 +26,7 @@ class SimpleTest extends Base
     /**
      * @group functional
      */
-    public function testConnection()
+    public function testConnection(): void
     {
         $client = $this->_getClient();
         $response = $client->request('_aliases');
@@ -37,7 +39,7 @@ public function testConnection()
     /**
      * @group functional
      */
-    public function testFailConnection()
+    public function testFailConnection(): void
     {
         $this->expectException(\Elastica\Exception\ConnectionException::class);
 
@@ -52,7 +54,7 @@ public function testFailConnection()
     /**
      * @group functional
      */
-    public function testWithOneFailConnection()
+    public function testWithOneFailConnection(): void
     {
         $connections = [
             new Connection(['host' => '255.255.255.0', 'timeout' => $this->_timeout]),
@@ -60,7 +62,7 @@ public function testWithOneFailConnection()
         ];
 
         $count = 0;
-        $callback = function ($connection, $exception, $client) use (&$count) {
+        $callback = function ($connection, $exception, $client) use (&$count): void {
             ++$count;
         };
 
@@ -80,7 +82,7 @@ public function testWithOneFailConnection()
     /**
      * @group functional
      */
-    public function testWithNoValidConnection()
+    public function testWithNoValidConnection(): void
     {
         $connections = [
             new Connection(['host' => '255.255.255.0', 'timeout' => $this->_timeout]),
@@ -89,7 +91,7 @@ public function testWithNoValidConnection()
         ];
 
         $count = 0;
-        $client = $this->_getClient([], function () use (&$count) {
+        $client = $this->_getClient([], function () use (&$count): void {
             ++$count;
         });
 
@@ -103,14 +105,14 @@ public function testWithNoValidConnection()
         }
     }
 
-    protected function _checkStrategy(Client $client)
+    protected function _checkStrategy(Client $client): void
     {
         $strategy = $client->getConnectionStrategy();
 
         $this->assertInstanceOf(Simple::class, $strategy);
     }
 
-    protected function _checkResponse(Response $response)
+    protected function _checkResponse(Response $response): void
     {
         $this->assertTrue($response->isOk());
     }
diff --git a/tests/Connection/Strategy/StrategyFactoryTest.php b/tests/Connection/Strategy/StrategyFactoryTest.php
index 019cbdd088..3deccb99a0 100644
--- a/tests/Connection/Strategy/StrategyFactoryTest.php
+++ b/tests/Connection/Strategy/StrategyFactoryTest.php
@@ -11,15 +11,17 @@
  * Description of StrategyFactoryTest.
  *
  * @author chabior
+ *
+ * @internal
  */
 class StrategyFactoryTest extends Base
 {
     /**
      * @group unit
      */
-    public function testCreateCallbackStrategy()
+    public function testCreateCallbackStrategy(): void
     {
-        $callback = function ($connections) {
+        $callback = function ($connections): void {
         };
 
         $strategy = StrategyFactory::create($callback);
@@ -30,7 +32,7 @@ public function testCreateCallbackStrategy()
     /**
      * @group unit
      */
-    public function testCreateByName()
+    public function testCreateByName(): void
     {
         $strategyName = 'Simple';
 
@@ -42,7 +44,7 @@ public function testCreateByName()
     /**
      * @group unit
      */
-    public function testCreateByClass()
+    public function testCreateByClass(): void
     {
         $strategy = new EmptyStrategy();
 
@@ -52,7 +54,7 @@ public function testCreateByClass()
     /**
      * @group unit
      */
-    public function testCreateByClassName()
+    public function testCreateByClassName(): void
     {
         $strategy = StrategyFactory::create(EmptyStrategy::class);
 
@@ -62,7 +64,7 @@ public function testCreateByClassName()
     /**
      * @group unit
      */
-    public function testFailCreate()
+    public function testFailCreate(): void
     {
         $this->expectException(\InvalidArgumentException::class);
 
@@ -74,7 +76,7 @@ public function testFailCreate()
     /**
      * @group unit
      */
-    public function testNoCollisionWithGlobalNamespace()
+    public function testNoCollisionWithGlobalNamespace(): void
     {
         // create collision
         if (!\class_exists('Simple')) {
diff --git a/tests/ConnectionTest.php b/tests/ConnectionTest.php
index f2fe62e072..1c00f6d7e4 100644
--- a/tests/ConnectionTest.php
+++ b/tests/ConnectionTest.php
@@ -9,12 +9,15 @@
 use Elastica\Transport\AbstractTransport;
 use Elastica\Transport\Http;
 
+/**
+ * @internal
+ */
 class ConnectionTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testEmptyConstructor()
+    public function testEmptyConstructor(): void
     {
         $connection = new Connection();
         $this->assertEquals(Connection::DEFAULT_HOST, $connection->getHost());
@@ -30,7 +33,7 @@ public function testEmptyConstructor()
     /**
      * @group unit
      */
-    public function testEnabledDisable()
+    public function testEnabledDisable(): void
     {
         $connection = new Connection();
         $this->assertTrue($connection->isEnabled());
@@ -43,7 +46,7 @@ public function testEnabledDisable()
     /**
      * @group unit
      */
-    public function testInvalidConnection()
+    public function testInvalidConnection(): void
     {
         $this->expectException(\Elastica\Exception\ConnectionException::class);
 
@@ -59,7 +62,7 @@ public function testInvalidConnection()
     /**
      * @group unit
      */
-    public function testCreate()
+    public function testCreate(): void
     {
         $connection = Connection::create();
         $this->assertInstanceOf(Connection::class, $connection);
@@ -76,7 +79,7 @@ public function testCreate()
     /**
      * @group unit
      */
-    public function testCreateInvalid()
+    public function testCreateInvalid(): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
 
@@ -86,7 +89,7 @@ public function testCreateInvalid()
     /**
      * @group unit
      */
-    public function testGetConfig()
+    public function testGetConfig(): void
     {
         $url = 'test';
         $connection = new Connection(['config' => ['url' => $url]]);
@@ -97,7 +100,7 @@ public function testGetConfig()
     /**
      * @group unit
      */
-    public function testGetConfigWithArrayUsedForTransport()
+    public function testGetConfigWithArrayUsedForTransport(): void
     {
         $connection = new Connection(['transport' => ['type' => 'Http']]);
         $this->assertInstanceOf(Http::class, $connection->getTransportObject());
@@ -106,7 +109,7 @@ public function testGetConfigWithArrayUsedForTransport()
     /**
      * @group unit
      */
-    public function testGetInvalidConfigWithArrayUsedForTransport()
+    public function testGetInvalidConfigWithArrayUsedForTransport(): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
         $this->expectExceptionMessage('Invalid transport');
@@ -118,7 +121,7 @@ public function testGetInvalidConfigWithArrayUsedForTransport()
     /**
      * @group unit
      */
-    public function testGetConfigInvalidValue()
+    public function testGetConfigInvalidValue(): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
 
@@ -129,7 +132,7 @@ public function testGetConfigInvalidValue()
     /**
      * @group unit
      */
-    public function testCompression()
+    public function testCompression(): void
     {
         $connection = new Connection();
 
@@ -141,7 +144,7 @@ public function testCompression()
     /**
      * @group unit
      */
-    public function testCompressionDefaultWithClient()
+    public function testCompressionDefaultWithClient(): void
     {
         $client = new Client();
         $connection = $client->getConnection();
@@ -151,7 +154,7 @@ public function testCompressionDefaultWithClient()
     /**
      * @group unit
      */
-    public function testCompressionEnabledWithClient()
+    public function testCompressionEnabledWithClient(): void
     {
         $client = new Client(['connections' => [['compression' => true]]]);
         $connection = $client->getConnection();
@@ -162,7 +165,7 @@ public function testCompressionEnabledWithClient()
     /**
      * @group unit
      */
-    public function testUsernameFromClient()
+    public function testUsernameFromClient(): void
     {
         $username = 'foo';
         $client = new Client(['username' => $username]);
@@ -173,7 +176,7 @@ public function testUsernameFromClient()
     /**
      * @group unit
      */
-    public function testPasswordFromClient()
+    public function testPasswordFromClient(): void
     {
         $password = 'bar';
         $client = new Client(['password' => $password]);
diff --git a/tests/DeprecatedClassBase.php b/tests/DeprecatedClassBase.php
index 45f9ddb432..483d13a88d 100644
--- a/tests/DeprecatedClassBase.php
+++ b/tests/DeprecatedClassBase.php
@@ -9,13 +9,13 @@
  */
 class DeprecatedClassBase extends Base
 {
-    protected function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
         $this->hideDeprecated();
     }
 
-    protected function tearDown()
+    protected function tearDown(): void
     {
         $this->showDeprecated();
         parent::tearDown();
diff --git a/tests/DocumentTest.php b/tests/DocumentTest.php
index 1dc1bc82db..b18e1406a9 100644
--- a/tests/DocumentTest.php
+++ b/tests/DocumentTest.php
@@ -7,12 +7,15 @@
 use Elastica\Index;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class DocumentTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testAddFile()
+    public function testAddFile(): void
     {
         $fileName = '/dev/null';
         if (!\file_exists($fileName)) {
@@ -26,7 +29,7 @@ public function testAddFile()
     /**
      * @group unit
      */
-    public function testAddGeoPoint()
+    public function testAddGeoPoint(): void
     {
         $doc = new Document();
         $returnValue = $doc->addGeoPoint('point', 38.89859, -77.035971);
@@ -36,7 +39,7 @@ public function testAddGeoPoint()
     /**
      * @group unit
      */
-    public function testSetData()
+    public function testSetData(): void
     {
         $doc = new Document();
         $returnValue = $doc->setData(['data']);
@@ -46,7 +49,7 @@ public function testSetData()
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $id = '17';
         $data = ['hello' => 'world'];
@@ -65,7 +68,7 @@ public function testToArray()
     /**
      * @group unit
      */
-    public function testSetIndex()
+    public function testSetIndex(): void
     {
         $document = new Document();
         $document->setIndex('index2');
@@ -81,7 +84,7 @@ public function testSetIndex()
     /**
      * @group unit
      */
-    public function testHasId()
+    public function testHasId(): void
     {
         $document = new Document();
         $this->assertFalse($document->hasId());
@@ -96,7 +99,7 @@ public function testHasId()
     /**
      * @group unit
      */
-    public function testGetSetHasRefresh()
+    public function testGetSetHasRefresh(): void
     {
         $document = new Document();
         $this->assertFalse($document->hasRefresh());
@@ -120,7 +123,7 @@ public function testGetSetHasRefresh()
     /**
      * @group unit
      */
-    public function testGetOptions()
+    public function testGetOptions(): void
     {
         $document = new Document();
         $document->setIndex('index');
@@ -146,7 +149,7 @@ public function testGetOptions()
     /**
      * @group unit
      */
-    public function testGetSetHasRemove()
+    public function testGetSetHasRemove(): void
     {
         $document = new Document(1, ['field1' => 'value1', 'field2' => 'value2', 'field3' => 'value3', 'field4' => null]);
 
@@ -200,7 +203,7 @@ public function testGetSetHasRemove()
     /**
      * @group unit
      */
-    public function testDataPropertiesOverloading()
+    public function testDataPropertiesOverloading(): void
     {
         $document = new Document(1, ['field1' => 'value1', 'field2' => 'value2', 'field3' => 'value3', 'field4' => null]);
 
@@ -252,7 +255,7 @@ public function testDataPropertiesOverloading()
     /**
      * @group unit
      */
-    public function testSerializedData()
+    public function testSerializedData(): void
     {
         $data = '{"user":"rolf"}';
         $document = new Document(1, $data);
@@ -284,7 +287,7 @@ public function testSerializedData()
     /**
      * @group unit
      */
-    public function testUpsert()
+    public function testUpsert(): void
     {
         $document = new Document();
 
@@ -302,7 +305,7 @@ public function testUpsert()
     /**
      * @group unit
      */
-    public function testDocAsUpsert()
+    public function testDocAsUpsert(): void
     {
         $document = new Document();
 
diff --git a/tests/ErrorsCollector.php b/tests/ErrorsCollector.php
index c2bc0d62c4..3716d32724 100644
--- a/tests/ErrorsCollector.php
+++ b/tests/ErrorsCollector.php
@@ -23,7 +23,7 @@ public function __construct(?TestCase $testCase = null)
         $this->testCase = $testCase;
     }
 
-    public function add($error)
+    public function add($error): void
     {
         $this->errors[] = $error;
     }
@@ -33,14 +33,14 @@ public function getCount()
         return \count($this->errors);
     }
 
-    public function assertOnlyOneDeprecatedError($deprecationMessage)
+    public function assertOnlyOneDeprecatedError($deprecationMessage): void
     {
         $this->testCase->assertSame(1, $this->getCount());
         $this->testCase->assertSame(1, $this->getDeprecatedCount());
         $this->testCase->assertSame($deprecationMessage, $this->getMessage(0));
     }
 
-    public function assertOnlyDeprecatedErrors(array $deprecationMessages)
+    public function assertOnlyDeprecatedErrors(array $deprecationMessages): void
     {
         $this->testCase->assertSame(\count($deprecationMessages), $this->getCount());
         $this->testCase->assertSame(\count($deprecationMessages), $this->getDeprecatedCount());
diff --git a/tests/ExampleTest.php b/tests/ExampleTest.php
index b46f79d47c..c45957561a 100644
--- a/tests/ExampleTest.php
+++ b/tests/ExampleTest.php
@@ -7,13 +7,15 @@
 
 /**
  * Tests the example code.
+ *
+ * @internal
  */
 class ExampleTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testBasicGettingStarted()
+    public function testBasicGettingStarted(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('ruflin');
@@ -28,7 +30,7 @@ public function testBasicGettingStarted()
     /**
      * @group functional
      */
-    public function testExample()
+    public function testExample(): void
     {
         // Creates a new index 'xodoa' and a type 'user' inside this index
         $client = $this->_getClient();
diff --git a/tests/Exception/AbstractExceptionTest.php b/tests/Exception/AbstractExceptionTest.php
index e57372d3ff..bba69c8782 100644
--- a/tests/Exception/AbstractExceptionTest.php
+++ b/tests/Exception/AbstractExceptionTest.php
@@ -7,27 +7,25 @@
 
 abstract class AbstractExceptionTest extends BaseTest
 {
-    protected function _getExceptionClass()
-    {
-        $reflection = new \ReflectionObject($this);
-
-        // Elastica\Test\Exception\RuntimeExceptionTest => Elastica\Exception\RuntimeExceptionTest
-        $name = \preg_replace('/^Elastica\\\\Test/', 'Elastica', $reflection->getName());
-
-        // Elastica\Exception\RuntimeExceptionTest => Elastica\Exception\RuntimeException
-        $name = \preg_replace('/Test$/', '', $name);
-
-        return $name;
-    }
-
     /**
      * @group unit
      */
-    public function testInheritance()
+    public function testInheritance(): void
     {
         $className = $this->_getExceptionClass();
         $reflection = new \ReflectionClass($className);
         $this->assertTrue($reflection->isSubclassOf(\Exception::class));
         $this->assertTrue($reflection->implementsInterface(ExceptionInterface::class));
     }
+
+    protected function _getExceptionClass()
+    {
+        $reflection = new \ReflectionObject($this);
+
+        // Elastica\Test\Exception\RuntimeExceptionTest => Elastica\Exception\RuntimeExceptionTest
+        $name = \preg_replace('/^Elastica\\\\Test/', 'Elastica', $reflection->getName());
+
+        // Elastica\Exception\RuntimeExceptionTest => Elastica\Exception\RuntimeException
+        return \preg_replace('/Test$/', '', $name);
+    }
 }
diff --git a/tests/Exception/Bulk/Response/ActionExceptionTest.php b/tests/Exception/Bulk/Response/ActionExceptionTest.php
index 184e1ba207..4d3a45aa56 100644
--- a/tests/Exception/Bulk/Response/ActionExceptionTest.php
+++ b/tests/Exception/Bulk/Response/ActionExceptionTest.php
@@ -4,6 +4,9 @@
 
 use Elastica\Test\Exception\AbstractExceptionTest;
 
+/**
+ * @internal
+ */
 class ActionExceptionTest extends AbstractExceptionTest
 {
 }
diff --git a/tests/Exception/Bulk/ResponseExceptionTest.php b/tests/Exception/Bulk/ResponseExceptionTest.php
index 7da6657b07..3b5d6b3ecc 100644
--- a/tests/Exception/Bulk/ResponseExceptionTest.php
+++ b/tests/Exception/Bulk/ResponseExceptionTest.php
@@ -4,6 +4,9 @@
 
 use Elastica\Test\Exception\AbstractExceptionTest;
 
+/**
+ * @internal
+ */
 class ResponseExceptionTest extends AbstractExceptionTest
 {
 }
diff --git a/tests/Exception/BulkExceptionTest.php b/tests/Exception/BulkExceptionTest.php
index 0374eb42a6..703e2d87f6 100644
--- a/tests/Exception/BulkExceptionTest.php
+++ b/tests/Exception/BulkExceptionTest.php
@@ -2,6 +2,9 @@
 
 namespace Elastica\Test\Exception;
 
+/**
+ * @internal
+ */
 class BulkExceptionTest extends AbstractExceptionTest
 {
 }
diff --git a/tests/Exception/ClientExceptionTest.php b/tests/Exception/ClientExceptionTest.php
index 06e8d45b11..95fe0c644d 100644
--- a/tests/Exception/ClientExceptionTest.php
+++ b/tests/Exception/ClientExceptionTest.php
@@ -2,6 +2,9 @@
 
 namespace Elastica\Test\Exception;
 
+/**
+ * @internal
+ */
 class ClientExceptionTest extends AbstractExceptionTest
 {
 }
diff --git a/tests/Exception/Connection/GuzzleExceptionTest.php b/tests/Exception/Connection/GuzzleExceptionTest.php
index c4c15816ce..3416df8f38 100644
--- a/tests/Exception/Connection/GuzzleExceptionTest.php
+++ b/tests/Exception/Connection/GuzzleExceptionTest.php
@@ -4,9 +4,12 @@
 
 use Elastica\Test\Exception\AbstractExceptionTest;
 
+/**
+ * @internal
+ */
 class GuzzleExceptionTest extends AbstractExceptionTest
 {
-    public static function setUpBeforeClass()
+    public static function setUpBeforeClass(): void
     {
         if (!\class_exists('GuzzleHttp\\Client')) {
             self::markTestSkipped('guzzlehttp/guzzle package should be installed to run guzzle transport tests');
diff --git a/tests/Exception/Connection/HttpExceptionTest.php b/tests/Exception/Connection/HttpExceptionTest.php
index 701d6770c8..5b3747316b 100644
--- a/tests/Exception/Connection/HttpExceptionTest.php
+++ b/tests/Exception/Connection/HttpExceptionTest.php
@@ -4,6 +4,9 @@
 
 use Elastica\Test\Exception\AbstractExceptionTest;
 
+/**
+ * @internal
+ */
 class HttpExceptionTest extends AbstractExceptionTest
 {
 }
diff --git a/tests/Exception/ConnectionExceptionTest.php b/tests/Exception/ConnectionExceptionTest.php
index e7aeb61fba..895d29ae91 100644
--- a/tests/Exception/ConnectionExceptionTest.php
+++ b/tests/Exception/ConnectionExceptionTest.php
@@ -2,6 +2,9 @@
 
 namespace Elastica\Test\Exception;
 
+/**
+ * @internal
+ */
 class ConnectionExceptionTest extends AbstractExceptionTest
 {
 }
diff --git a/tests/Exception/InvalidExceptionTest.php b/tests/Exception/InvalidExceptionTest.php
index 0b35a579fb..b29732ef38 100644
--- a/tests/Exception/InvalidExceptionTest.php
+++ b/tests/Exception/InvalidExceptionTest.php
@@ -2,6 +2,9 @@
 
 namespace Elastica\Test\Exception;
 
+/**
+ * @internal
+ */
 class InvalidExceptionTest extends AbstractExceptionTest
 {
 }
diff --git a/tests/Exception/JSONParseExceptionTest.php b/tests/Exception/JSONParseExceptionTest.php
index c6ba7d825d..3d36de7622 100644
--- a/tests/Exception/JSONParseExceptionTest.php
+++ b/tests/Exception/JSONParseExceptionTest.php
@@ -2,6 +2,9 @@
 
 namespace Elastica\Test\Exception;
 
+/**
+ * @internal
+ */
 class JSONParseExceptionTest extends AbstractExceptionTest
 {
 }
diff --git a/tests/Exception/NotFoundExceptionTest.php b/tests/Exception/NotFoundExceptionTest.php
index c85bdb7a43..4461729d5d 100644
--- a/tests/Exception/NotFoundExceptionTest.php
+++ b/tests/Exception/NotFoundExceptionTest.php
@@ -2,6 +2,9 @@
 
 namespace Elastica\Test\Exception;
 
+/**
+ * @internal
+ */
 class NotFoundExceptionTest extends AbstractExceptionTest
 {
 }
diff --git a/tests/Exception/NotImplementedExceptionTest.php b/tests/Exception/NotImplementedExceptionTest.php
index c04dc3c6ba..a8db701b64 100644
--- a/tests/Exception/NotImplementedExceptionTest.php
+++ b/tests/Exception/NotImplementedExceptionTest.php
@@ -4,12 +4,15 @@
 
 use Elastica\Exception\NotImplementedException;
 
+/**
+ * @internal
+ */
 class NotImplementedExceptionTest extends AbstractExceptionTest
 {
     /**
      * @group unit
      */
-    public function testInstance()
+    public function testInstance(): void
     {
         $code = 4;
         $message = 'Hello world';
diff --git a/tests/Exception/PartialShardFailureExceptionTest.php b/tests/Exception/PartialShardFailureExceptionTest.php
index cab2bda564..5b4c21f8b7 100644
--- a/tests/Exception/PartialShardFailureExceptionTest.php
+++ b/tests/Exception/PartialShardFailureExceptionTest.php
@@ -8,12 +8,15 @@
 use Elastica\Query;
 use Elastica\ResultSet\DefaultBuilder;
 
+/**
+ * @internal
+ */
 class PartialShardFailureExceptionTest extends AbstractExceptionTest
 {
     /**
      * @group functional
      */
-    public function testPartialFailure()
+    public function testPartialFailure(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('elastica_partial_failure');
@@ -23,9 +26,11 @@ public function testPartialFailure()
                     'index' => [
                         'number_of_shards' => 5,
                         'number_of_replicas' => 0,
-                        ],
                     ],
-           ], true);
+                ],
+            ],
+            true
+        );
 
         $index->addDocument(new Document('', ['name' => 'ruflin']));
         $index->addDocument(new Document('', ['name' => 'bobrik']));
diff --git a/tests/Exception/QueryBuilderExceptionTest.php b/tests/Exception/QueryBuilderExceptionTest.php
index e38afa2230..168e766d89 100644
--- a/tests/Exception/QueryBuilderExceptionTest.php
+++ b/tests/Exception/QueryBuilderExceptionTest.php
@@ -2,6 +2,9 @@
 
 namespace Elastica\Test\Exception;
 
+/**
+ * @internal
+ */
 class QueryBuilderExceptionTest extends AbstractExceptionTest
 {
 }
diff --git a/tests/Exception/ResponseExceptionTest.php b/tests/Exception/ResponseExceptionTest.php
index 4150075428..50ea32e65a 100644
--- a/tests/Exception/ResponseExceptionTest.php
+++ b/tests/Exception/ResponseExceptionTest.php
@@ -6,12 +6,15 @@
 use Elastica\Exception\ResponseException;
 use Elastica\Mapping;
 
+/**
+ * @internal
+ */
 class ResponseExceptionTest extends AbstractExceptionTest
 {
     /**
      * @group functional
      */
-    public function testCreateExistingIndex()
+    public function testCreateExistingIndex(): void
     {
         $this->_createIndex('woo', true);
 
@@ -30,7 +33,7 @@ public function testCreateExistingIndex()
     /**
      * @group functional
      */
-    public function testBadType()
+    public function testBadType(): void
     {
         $index = $this->_createIndex();
 
@@ -55,7 +58,7 @@ public function testBadType()
     /**
      * @group functional
      */
-    public function testWhatever()
+    public function testWhatever(): void
     {
         $index = $this->_createIndex();
         $index->delete();
diff --git a/tests/Exception/RuntimeExceptionTest.php b/tests/Exception/RuntimeExceptionTest.php
index 2f08a3818d..fd5c3cd5f7 100644
--- a/tests/Exception/RuntimeExceptionTest.php
+++ b/tests/Exception/RuntimeExceptionTest.php
@@ -2,6 +2,9 @@
 
 namespace Elastica\Test\Exception;
 
+/**
+ * @internal
+ */
 class RuntimeExceptionTest extends AbstractExceptionTest
 {
 }
diff --git a/tests/Index/RecoveryTest.php b/tests/Index/RecoveryTest.php
index bb6b6d5710..b7d015f5bf 100644
--- a/tests/Index/RecoveryTest.php
+++ b/tests/Index/RecoveryTest.php
@@ -5,12 +5,15 @@
 use Elastica\Index\Recovery;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class RecoveryTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testGetSettings()
+    public function testGetSettings(): void
     {
         $indexName = 'test';
 
diff --git a/tests/Index/SettingsTest.php b/tests/Index/SettingsTest.php
index b2690ecfb9..226b759f5e 100644
--- a/tests/Index/SettingsTest.php
+++ b/tests/Index/SettingsTest.php
@@ -9,12 +9,15 @@
 use Elastica\Response;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class SettingsTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testGet()
+    public function testGet(): void
     {
         $indexName = 'elasticatest';
 
@@ -35,7 +38,7 @@ public function testGet()
     /**
      * @group functional
      */
-    public function testGetWithAlias()
+    public function testGetWithAlias(): void
     {
         $indexName = 'elasticatest';
         $aliasName = 'elasticatest_alias';
@@ -61,7 +64,7 @@ public function testGetWithAlias()
     /**
      * @group functional
      */
-    public function testDeleteAliasWithException()
+    public function testDeleteAliasWithException(): void
     {
         $indexName = 'deletetestaliasexception';
         $aliasName = 'deletetestaliasexception_alias';
@@ -88,7 +91,7 @@ public function testDeleteAliasWithException()
     /**
      * @group functional
      */
-    public function testSetGetNumberOfReplicas()
+    public function testSetGetNumberOfReplicas(): void
     {
         $index = $this->_createIndex();
         $index->create([], true);
@@ -112,7 +115,7 @@ public function testSetGetNumberOfReplicas()
     /**
      * @group functional
      */
-    public function testGetNumberOfReplicas()
+    public function testGetNumberOfReplicas(): void
     {
         $index = $this->_createIndex();
         $index->create([], true);
@@ -129,7 +132,7 @@ public function testGetNumberOfReplicas()
     /**
      * @group functional
      */
-    public function testGetNumberOfShards()
+    public function testGetNumberOfShards(): void
     {
         $index = $this->_createIndex();
         $index->create([], true);
@@ -146,7 +149,7 @@ public function testGetNumberOfShards()
     /**
      * @group functional
      */
-    public function testGetDefaultNumberOfShards()
+    public function testGetDefaultNumberOfShards(): void
     {
         $index = $this->_createIndex();
         $index->create([], true);
@@ -164,7 +167,7 @@ public function testGetDefaultNumberOfShards()
     /**
      * @group functional
      */
-    public function testSetRefreshInterval()
+    public function testSetRefreshInterval(): void
     {
         $index = $this->_createIndex();
         $index->create([], true);
@@ -185,7 +188,7 @@ public function testSetRefreshInterval()
     /**
      * @group functional
      */
-    public function testGetRefreshInterval()
+    public function testGetRefreshInterval(): void
     {
         $index = $this->_createIndex();
         $index->create([], true);
@@ -206,7 +209,7 @@ public function testGetRefreshInterval()
     /**
      * @group functional
      */
-    public function testSetMergePolicy()
+    public function testSetMergePolicy(): void
     {
         $index = $this->_createIndex();
         $index->create([], true);
@@ -227,7 +230,7 @@ public function testSetMergePolicy()
     /**
      * @group functional
      */
-    public function testSetMaxMergeAtOnce()
+    public function testSetMaxMergeAtOnce(): void
     {
         $index = $this->_createIndex();
         $index->create([], true);
@@ -251,7 +254,7 @@ public function testSetMaxMergeAtOnce()
     /**
      * @group functional
      */
-    public function testSetReadOnly()
+    public function testSetReadOnly(): void
     {
         $index = $this->_createIndex();
         //wait for the shards to be allocated
@@ -296,7 +299,7 @@ public function testSetReadOnly()
     /**
      * @group functional
      */
-    public function testGetSetBlocksRead()
+    public function testGetSetBlocksRead(): void
     {
         $index = $this->_createIndex();
         $index->refresh();
@@ -319,7 +322,7 @@ public function testGetSetBlocksRead()
     /**
      * @group functional
      */
-    public function testGetSetBlocksWrite()
+    public function testGetSetBlocksWrite(): void
     {
         $index = $this->_createIndex();
         $index->refresh();
@@ -342,7 +345,7 @@ public function testGetSetBlocksWrite()
     /**
      * @group functional
      */
-    public function testGetSetBlocksMetadata()
+    public function testGetSetBlocksMetadata(): void
     {
         $index = $this->_createIndex();
         $index->refresh();
@@ -367,7 +370,7 @@ public function testGetSetBlocksMetadata()
     /**
      * @group functional
      */
-    public function testNotFoundIndex()
+    public function testNotFoundIndex(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('not_found_index');
@@ -385,7 +388,7 @@ public function testNotFoundIndex()
     /**
      * @group functional
      */
-    public function testSetMultiple()
+    public function testSetMultiple(): void
     {
         $index = $this->_createIndex();
         $index->create([], true);
diff --git a/tests/Index/StatsTest.php b/tests/Index/StatsTest.php
index ccda2d7959..1236ce6936 100644
--- a/tests/Index/StatsTest.php
+++ b/tests/Index/StatsTest.php
@@ -5,12 +5,15 @@
 use Elastica\Index\Stats;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class StatsTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testGetSettings()
+    public function testGetSettings(): void
     {
         $indexName = 'test';
 
diff --git a/tests/IndexTemplateTest.php b/tests/IndexTemplateTest.php
index bef28b7431..beead485e7 100644
--- a/tests/IndexTemplateTest.php
+++ b/tests/IndexTemplateTest.php
@@ -13,13 +13,15 @@
  * IndexTemplate class tests.
  *
  * @author Dmitry Balabka <dmitry.balabka@intexsys.lv>
+ *
+ * @internal
  */
 class IndexTemplateTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testInstantiate()
+    public function testInstantiate(): void
     {
         $name = 'index_template1';
         $client = $this->_getClient();
@@ -32,7 +34,7 @@ public function testInstantiate()
     /**
      * @group unit
      */
-    public function testIncorrectInstantiate()
+    public function testIncorrectInstantiate(): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
 
@@ -43,16 +45,17 @@ public function testIncorrectInstantiate()
     /**
      * @group unit
      */
-    public function testDelete()
+    public function testDelete(): void
     {
         $name = 'index_template1';
         $response = new Response('');
-        /** @var \PHPUnit_Framework_MockObject_MockObject|Client $clientMock */
+        /** @var Client|\PHPUnit_Framework_MockObject_MockObject $clientMock */
         $clientMock = $this->createMock(Client::class);
         $clientMock->expects($this->once())
             ->method('request')
             ->with('_template/'.$name, Request::DELETE, [], [])
-            ->willReturn($response);
+            ->willReturn($response)
+        ;
         $indexTemplate = new IndexTemplate($clientMock, $name);
         $this->assertSame($response, $indexTemplate->delete());
     }
@@ -60,17 +63,18 @@ public function testDelete()
     /**
      * @group unit
      */
-    public function testCreate()
+    public function testCreate(): void
     {
         $args = [1];
         $response = new Response('');
         $name = 'index_template1';
-        /** @var \PHPUnit_Framework_MockObject_MockObject|Client $clientMock */
+        /** @var Client|\PHPUnit_Framework_MockObject_MockObject $clientMock */
         $clientMock = $this->createMock(Client::class);
         $clientMock->expects($this->once())
             ->method('request')
             ->with('_template/'.$name, Request::PUT, $args, [])
-            ->willReturn($response);
+            ->willReturn($response)
+        ;
         $indexTemplate = new IndexTemplate($clientMock, $name);
         $this->assertSame($response, $indexTemplate->create($args));
     }
@@ -78,16 +82,17 @@ public function testCreate()
     /**
      * @group unit
      */
-    public function testExists()
+    public function testExists(): void
     {
         $name = 'index_template1';
         $response = new Response('', 200);
-        /** @var \PHPUnit_Framework_MockObject_MockObject|Client $clientMock */
+        /** @var Client|\PHPUnit_Framework_MockObject_MockObject $clientMock */
         $clientMock = $this->createMock(Client::class);
         $clientMock->expects($this->once())
             ->method('request')
             ->with('_template/'.$name, Request::HEAD, [], [])
-            ->willReturn($response);
+            ->willReturn($response)
+        ;
         $indexTemplate = new IndexTemplate($clientMock, $name);
         $this->assertTrue($indexTemplate->exists());
     }
@@ -95,7 +100,7 @@ public function testExists()
     /**
      * @group functional
      */
-    public function testCreateTemplate()
+    public function testCreateTemplate(): void
     {
         $template = [
             'index_patterns' => 'te*',
@@ -114,7 +119,7 @@ public function testCreateTemplate()
     /**
      * @group functional
      */
-    public function testCreateAlreadyExistsTemplateException()
+    public function testCreateAlreadyExistsTemplateException(): void
     {
         $template = [
             'index_patterns' => 'te*',
diff --git a/tests/IndexTest.php b/tests/IndexTest.php
index 7d6b9c4514..8aceb07c7f 100644
--- a/tests/IndexTest.php
+++ b/tests/IndexTest.php
@@ -18,6 +18,8 @@
 
 /**
  * @group functional
+ *
+ * @internal
  */
 class IndexTest extends BaseTest
 {
diff --git a/tests/JSONTest.php b/tests/JSONTest.php
index 3ce7ee4691..c0962126bd 100644
--- a/tests/JSONTest.php
+++ b/tests/JSONTest.php
@@ -9,16 +9,18 @@
  * JSONTest.
  *
  * @author Oleg Andreyev <oleg.andreyev@intexsys.lv>
+ *
+ * @internal
  */
 class JSONTest extends TestCase
 {
-    public function testStringifyMustNotThrowExceptionOnValid()
+    public function testStringifyMustNotThrowExceptionOnValid(): void
     {
         JSON::stringify([]);
         $this->assertTrue(true);
     }
 
-    public function testStringifyMustThrowExceptionNanOrInf()
+    public function testStringifyMustThrowExceptionNanOrInf(): void
     {
         $this->expectException(\Elastica\Exception\JSONParseException::class);
         $this->expectExceptionMessage('Inf and NaN cannot be JSON encoded');
@@ -28,7 +30,7 @@ public function testStringifyMustThrowExceptionNanOrInf()
         $this->assertTrue(true);
     }
 
-    public function testStringifyMustThrowExceptionMaximumDepth()
+    public function testStringifyMustThrowExceptionMaximumDepth(): void
     {
         $this->expectException(\Elastica\Exception\JSONParseException::class);
         $this->expectExceptionMessage('Maximum stack depth exceeded');
diff --git a/tests/MappingTest.php b/tests/MappingTest.php
index ec2c949b7d..b3fef5a9ab 100644
--- a/tests/MappingTest.php
+++ b/tests/MappingTest.php
@@ -8,12 +8,15 @@
 use Elastica\Query\QueryString;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class MappingTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testMappingStoreFields()
+    public function testMappingStoreFields(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('test');
@@ -30,7 +33,8 @@ public function testMappingStoreFields()
         $index->setMapping($mapping);
 
         $firstname = 'Nicolas';
-        $doc = new Document(1,
+        $doc = new Document(
+            1,
             [
                 'firstname' => $firstname,
                 'lastname' => 'Ruflin',
@@ -63,7 +67,7 @@ public function testMappingStoreFields()
     /**
      * @group functional
      */
-    public function testNestedMapping()
+    public function testNestedMapping(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('test');
@@ -103,7 +107,7 @@ public function testNestedMapping()
     /**
      * @group functional
      */
-    public function testJoinMapping()
+    public function testJoinMapping(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('testjoinparentid');
@@ -122,15 +126,15 @@ public function testJoinMapping()
 
         $expected = [
             'properties' => [
-                  'firstname' => ['type' => 'text', 'store' => true],
-                  'lastname' => ['type' => 'text'],
-                  'my_join_field' => [
-                      'type' => 'join',
-                      'relations' => [
-                          'question' => 'answer',
-                      ],
-                  ],
-              ],
+                'firstname' => ['type' => 'text', 'store' => true],
+                'lastname' => ['type' => 'text'],
+                'my_join_field' => [
+                    'type' => 'join',
+                    'relations' => [
+                        'question' => 'answer',
+                    ],
+                ],
+            ],
         ];
 
         $this->assertEquals($expected, $mapping->toArray());
@@ -182,7 +186,7 @@ public function testJoinMapping()
     /**
      * @group functional
      */
-    public function testMappingExample()
+    public function testMappingExample(): void
     {
         $index = $this->_createIndex();
 
@@ -198,7 +202,9 @@ public function testMappingExample()
 
         $index->setMapping($mapping);
 
-        $doc = new Document(1, [
+        $doc = new Document(
+            1,
+            [
                 'note' => [
                     [
                         'titulo' => 'nota1',
@@ -225,7 +231,7 @@ public function testMappingExample()
      *
      * @see https://www.elastic.co/guide/en/elasticsearch/reference/current/dynamic-templates.html
      */
-    public function testDynamicTemplate()
+    public function testDynamicTemplate(): void
     {
         $index = $this->_createIndex();
 
@@ -277,7 +283,7 @@ public function testDynamicTemplate()
     /**
      * @group functional
      */
-    public function testSetMeta()
+    public function testSetMeta(): void
     {
         $index = $this->_createIndex();
         $mapping = new Mapping([
@@ -297,7 +303,7 @@ public function testSetMeta()
     /**
      * @group functional
      */
-    public function testGetters()
+    public function testGetters(): void
     {
         $properties = [
             'firstname' => ['type' => 'text', 'store' => true],
diff --git a/tests/Multi/MultiBuilderTest.php b/tests/Multi/MultiBuilderTest.php
index 752a40298c..642a4690af 100644
--- a/tests/Multi/MultiBuilderTest.php
+++ b/tests/Multi/MultiBuilderTest.php
@@ -12,6 +12,8 @@
 
 /**
  * @group unit
+ *
+ * @internal
  */
 class MultiBuilderTest extends BaseTest
 {
@@ -25,7 +27,7 @@ class MultiBuilderTest extends BaseTest
      */
     private $multiBuilder;
 
-    protected function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
 
@@ -33,10 +35,11 @@ protected function setUp()
         $this->multiBuilder = new MultiBuilder();
     }
 
-    public function testBuildEmptyMultiResultSet()
+    public function testBuildEmptyMultiResultSet(): void
     {
         $this->builder->expects($this->never())
-            ->method('buildResultSet');
+            ->method('buildResultSet')
+        ;
 
         $response = new Response([]);
         $searches = [];
@@ -46,7 +49,7 @@ public function testBuildEmptyMultiResultSet()
         $this->assertInstanceOf(MultiResultSet::class, $result);
     }
 
-    public function testBuildMultiResultSet()
+    public function testBuildMultiResultSet(): void
     {
         $response = new Response([
             'responses' => [
@@ -67,7 +70,8 @@ public function testBuildMultiResultSet()
                 [$this->isInstanceOf(Response::class), $s1->getQuery()],
                 [$this->isInstanceOf(Response::class), $s2->getQuery()]
             )
-            ->willReturnOnConsecutiveCalls($resultSet1, $resultSet2);
+            ->willReturnOnConsecutiveCalls($resultSet1, $resultSet2)
+        ;
 
         $result = $this->multiBuilder->buildMultiResultSet($response, $searches);
 
diff --git a/tests/Multi/SearchTest.php b/tests/Multi/SearchTest.php
index e335a639b8..9463181d8d 100644
--- a/tests/Multi/SearchTest.php
+++ b/tests/Multi/SearchTest.php
@@ -13,37 +13,15 @@
 use Elastica\Search;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class SearchTest extends BaseTest
 {
-    protected function _createIndex(?string $name = null, bool $delete = true, int $shards = 1): Index
-    {
-        $client = $this->_getClient();
-
-        $index = $client->getIndex('zero');
-        $index->create(['settings' => ['index' => ['number_of_shards' => 1, 'number_of_replicas' => 0]]], true);
-
-        $docs = [];
-        $docs[] = new Document(1, ['id' => 1, 'email' => 'test@test.com', 'username' => 'farrelley']);
-        $docs[] = new Document(2, ['id' => 1, 'email' => 'test@test.com', 'username' => 'farrelley']);
-        $docs[] = new Document(3, ['id' => 1, 'email' => 'test@test.com', 'username' => 'farrelley']);
-        $docs[] = new Document(4, ['id' => 1, 'email' => 'test@test.com', 'username' => 'kate']);
-        $docs[] = new Document(5, ['id' => 1, 'email' => 'test@test.com', 'username' => 'kate']);
-        $docs[] = new Document(6, ['id' => 1, 'email' => 'test@test.com', 'username' => 'bunny']);
-        $docs[] = new Document(7, ['id' => 1, 'email' => 'test@test.com', 'username' => 'bunny']);
-        $docs[] = new Document(8, ['id' => 1, 'email' => 'test@test.com', 'username' => 'bunny']);
-        $docs[] = new Document(9, ['id' => 1, 'email' => 'test@test.com', 'username' => 'bunny']);
-        $docs[] = new Document(10, ['id' => 1, 'email' => 'test@test.com', 'username' => 'bunny']);
-        $docs[] = new Document(11, ['id' => 1, 'email' => 'test@test.com', 'username' => 'bunny']);
-        $index->addDocuments($docs);
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group unit
      */
-    public function testConstruct()
+    public function testConstruct(): void
     {
         $client = $this->_getClient();
         $multiSearch = new MultiSearch($client);
@@ -54,7 +32,7 @@ public function testConstruct()
     /**
      * @group unit
      */
-    public function testSetSearches()
+    public function testSetSearches(): void
     {
         $client = $this->_getClient();
         $multiSearch = new MultiSearch($client);
@@ -86,7 +64,7 @@ public function testSetSearches()
     /**
      * @group unit
      */
-    public function testSetSearchesByKeys()
+    public function testSetSearchesByKeys(): void
     {
         $client = $this->_getClient();
         $multiSearch = new MultiSearch($client);
@@ -118,7 +96,7 @@ public function testSetSearchesByKeys()
     /**
      * @group functional
      */
-    public function testSearch()
+    public function testSearch(): void
     {
         $index = $this->_createIndex();
         $client = $index->getClient();
@@ -208,7 +186,7 @@ public function testSearch()
     /**
      * @group functional
      */
-    public function testSearchWithKeys()
+    public function testSearchWithKeys(): void
     {
         $index = $this->_createIndex();
         $client = $index->getClient();
@@ -300,7 +278,7 @@ public function testSearchWithKeys()
     /**
      * @group functional
      */
-    public function testSearchWithError()
+    public function testSearchWithError(): void
     {
         $index = $this->_createIndex();
         $client = $index->getClient();
@@ -345,7 +323,7 @@ public function testSearchWithError()
     /**
      * @group functional
      */
-    public function testSearchWithErrorWithKeys()
+    public function testSearchWithErrorWithKeys(): void
     {
         $index = $this->_createIndex();
         $client = $index->getClient();
@@ -390,7 +368,7 @@ public function testSearchWithErrorWithKeys()
     /**
      * @group functional
      */
-    public function testGlobalSearchTypeSearch()
+    public function testGlobalSearchTypeSearch(): void
     {
         $index = $this->_createIndex();
         $client = $index->getClient();
@@ -473,7 +451,7 @@ public function testGlobalSearchTypeSearch()
     /**
      * @group functional
      */
-    public function testGlobalSearchTypeSearchWithKeys()
+    public function testGlobalSearchTypeSearchWithKeys(): void
     {
         $index = $this->_createIndex();
         $client = $index->getClient();
@@ -557,7 +535,7 @@ public function testGlobalSearchTypeSearchWithKeys()
     /**
      * @group functional
      */
-    public function testSearchWithSearchOptions()
+    public function testSearchWithSearchOptions(): void
     {
         $index = $this->_createIndex();
         $client = $index->getClient();
@@ -593,4 +571,29 @@ public function testSearchWithSearchOptions()
         $this->assertEquals(1, $resultSets[0]->getTotalHits());
         $this->assertEquals(6, $resultSets[1]->getTotalHits());
     }
+
+    protected function _createIndex(?string $name = null, bool $delete = true, int $shards = 1): Index
+    {
+        $client = $this->_getClient();
+
+        $index = $client->getIndex('zero');
+        $index->create(['settings' => ['index' => ['number_of_shards' => 1, 'number_of_replicas' => 0]]], true);
+
+        $docs = [];
+        $docs[] = new Document(1, ['id' => 1, 'email' => 'test@test.com', 'username' => 'farrelley']);
+        $docs[] = new Document(2, ['id' => 1, 'email' => 'test@test.com', 'username' => 'farrelley']);
+        $docs[] = new Document(3, ['id' => 1, 'email' => 'test@test.com', 'username' => 'farrelley']);
+        $docs[] = new Document(4, ['id' => 1, 'email' => 'test@test.com', 'username' => 'kate']);
+        $docs[] = new Document(5, ['id' => 1, 'email' => 'test@test.com', 'username' => 'kate']);
+        $docs[] = new Document(6, ['id' => 1, 'email' => 'test@test.com', 'username' => 'bunny']);
+        $docs[] = new Document(7, ['id' => 1, 'email' => 'test@test.com', 'username' => 'bunny']);
+        $docs[] = new Document(8, ['id' => 1, 'email' => 'test@test.com', 'username' => 'bunny']);
+        $docs[] = new Document(9, ['id' => 1, 'email' => 'test@test.com', 'username' => 'bunny']);
+        $docs[] = new Document(10, ['id' => 1, 'email' => 'test@test.com', 'username' => 'bunny']);
+        $docs[] = new Document(11, ['id' => 1, 'email' => 'test@test.com', 'username' => 'bunny']);
+        $index->addDocuments($docs);
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Node/InfoTest.php b/tests/Node/InfoTest.php
index a3f95810eb..81052ba676 100644
--- a/tests/Node/InfoTest.php
+++ b/tests/Node/InfoTest.php
@@ -6,12 +6,15 @@
 use Elastica\Node\Info as NodeInfo;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class InfoTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testGet()
+    public function testGet(): void
     {
         $client = $this->_getClient();
         $names = $client->getCluster()->getNodeNames();
@@ -35,7 +38,7 @@ public function testGet()
     /**
      * @group functional
      */
-    public function testHasPlugin()
+    public function testHasPlugin(): void
     {
         $client = $this->_getClient();
         $nodes = $client->getCluster()->getNodes();
@@ -49,7 +52,7 @@ public function testHasPlugin()
     /**
      * @group functional
      */
-    public function testGetId()
+    public function testGetId(): void
     {
         $client = $this->_getClient();
         $nodes = $client->getCluster()->getNodes();
@@ -68,7 +71,7 @@ public function testGetId()
     /**
      * @group functional
      */
-    public function testGetName()
+    public function testGetName(): void
     {
         $client = $this->_getClient();
 
@@ -85,7 +88,7 @@ public function testGetName()
     /**
      * @group functional
      */
-    public function testParams()
+    public function testParams(): void
     {
         $client = $this->_getClient();
 
diff --git a/tests/NodeTest.php b/tests/NodeTest.php
index 1add01eca3..d712214bc2 100644
--- a/tests/NodeTest.php
+++ b/tests/NodeTest.php
@@ -7,12 +7,15 @@
 use Elastica\Node\Stats;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class NodeTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testCreateNode()
+    public function testCreateNode(): void
     {
         $client = $this->_getClient();
         $names = $client->getCluster()->getNodeNames();
@@ -25,7 +28,7 @@ public function testCreateNode()
     /**
      * @group functional
      */
-    public function testGetInfo()
+    public function testGetInfo(): void
     {
         $client = $this->_getClient();
         $names = $client->getCluster()->getNodeNames();
@@ -41,7 +44,7 @@ public function testGetInfo()
     /**
      * @group functional
      */
-    public function testGetStats()
+    public function testGetStats(): void
     {
         $client = $this->_getClient();
         $names = $client->getCluster()->getNodeNames();
@@ -57,7 +60,7 @@ public function testGetStats()
     /**
      * @group functional
      */
-    public function testGetName()
+    public function testGetName(): void
     {
         $client = $this->_getClient();
 
@@ -76,7 +79,7 @@ public function testGetName()
     /**
      * @group functional
      */
-    public function testGetId()
+    public function testGetId(): void
     {
         $node = new Node('Elastica', $this->_getClient());
     }
diff --git a/tests/ParamTest.php b/tests/ParamTest.php
index 7460327808..4b5d0f120d 100644
--- a/tests/ParamTest.php
+++ b/tests/ParamTest.php
@@ -6,12 +6,15 @@
 use Elastica\Test\Base as BaseTest;
 use Elastica\Util;
 
+/**
+ * @internal
+ */
 class ParamTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArrayEmpty()
+    public function testToArrayEmpty(): void
     {
         $param = new Param();
         $this->assertInstanceOf(Param::class, $param);
@@ -21,7 +24,7 @@ public function testToArrayEmpty()
     /**
      * @group unit
      */
-    public function testSetParams()
+    public function testSetParams(): void
     {
         $param = new Param();
         $params = ['hello' => 'word', 'nicolas' => 'ruflin'];
@@ -34,7 +37,7 @@ public function testSetParams()
     /**
      * @group unit
      */
-    public function testSetGetParam()
+    public function testSetGetParam(): void
     {
         $param = new Param();
 
@@ -51,7 +54,7 @@ public function testSetGetParam()
     /**
      * @group unit
      */
-    public function testAddParam()
+    public function testAddParam(): void
     {
         $param = new Param();
 
@@ -67,7 +70,7 @@ public function testAddParam()
     /**
      * @group unit
      */
-    public function testAddParam2()
+    public function testAddParam2(): void
     {
         $param = new Param();
 
@@ -85,7 +88,7 @@ public function testAddParam2()
     /**
      * @group unit
      */
-    public function testGetParamInvalid()
+    public function testGetParamInvalid(): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
 
@@ -97,7 +100,7 @@ public function testGetParamInvalid()
     /**
      * @group unit
      */
-    public function testHasParam()
+    public function testHasParam(): void
     {
         $param = new Param();
 
diff --git a/tests/PipelineTest.php b/tests/PipelineTest.php
index 3e945ca226..6e6b93e675 100644
--- a/tests/PipelineTest.php
+++ b/tests/PipelineTest.php
@@ -10,12 +10,15 @@
 use Elastica\Processor\Set;
 use Elastica\Processor\Trim;
 
+/**
+ * @internal
+ */
 class PipelineTest extends BasePipeline
 {
     /**
      * @group unit
      */
-    public function testProcessor()
+    public function testProcessor(): void
     {
         $trim = new Trim('field1');
         $rename = new Rename('foo', 'target.field');
@@ -50,7 +53,7 @@ public function testProcessor()
     /**
      * @group functional
      */
-    public function testPipelineCreate()
+    public function testPipelineCreate(): void
     {
         $set = new Set('field4', 333);
         $trim = new Trim('field1');
@@ -77,7 +80,7 @@ public function testPipelineCreate()
     /**
      * @group functional
      */
-    public function testPipelineonIndex()
+    public function testPipelineonIndex(): void
     {
         $set = new Set('foo', 333);
 
@@ -119,7 +122,7 @@ public function testPipelineonIndex()
     /**
      * @group functional
      */
-    public function testDeletePipeline()
+    public function testDeletePipeline(): void
     {
         $pipeline = $this->_createPipeline();
         try {
diff --git a/tests/Processor/AppendTest.php b/tests/Processor/AppendTest.php
index 410bbf48a0..32e4a56d7f 100644
--- a/tests/Processor/AppendTest.php
+++ b/tests/Processor/AppendTest.php
@@ -8,12 +8,15 @@
 use Elastica\ResultSet;
 use Elastica\Test\BasePipeline as BasePipelineTest;
 
+/**
+ * @internal
+ */
 class AppendTest extends BasePipelineTest
 {
     /**
      * @group unit
      */
-    public function testAppendSingleValue()
+    public function testAppendSingleValue(): void
     {
         $processor = new Append('field1', 'item2');
 
@@ -30,7 +33,7 @@ public function testAppendSingleValue()
     /**
      * @group unit
      */
-    public function testAppendArray()
+    public function testAppendArray(): void
     {
         $processor = new Append('field1', ['item2', 'item3', 'item4']);
 
@@ -47,7 +50,7 @@ public function testAppendArray()
     /**
      * @group functional
      */
-    public function testAppend()
+    public function testAppend(): void
     {
         $append = new Append('foo', ['item2', 'item3', 'item4']);
 
diff --git a/tests/Processor/AttachmentTest.php b/tests/Processor/AttachmentTest.php
index ef006d82d7..47cca66a4e 100644
--- a/tests/Processor/AttachmentTest.php
+++ b/tests/Processor/AttachmentTest.php
@@ -10,6 +10,8 @@
 
 /**
  * @group functional
+ *
+ * @internal
  */
 class AttachmentTest extends BasePipelineTest
 {
diff --git a/tests/Processor/ConvertTest.php b/tests/Processor/ConvertTest.php
index 6bbecb870e..94b2122b5e 100644
--- a/tests/Processor/ConvertTest.php
+++ b/tests/Processor/ConvertTest.php
@@ -8,12 +8,15 @@
 use Elastica\ResultSet;
 use Elastica\Test\BasePipeline as BasePipelineTest;
 
+/**
+ * @internal
+ */
 class ConvertTest extends BasePipelineTest
 {
     /**
      * @group unit
      */
-    public function testConvert()
+    public function testConvert(): void
     {
         $processor = new Convert('foo', 'integer');
 
@@ -30,7 +33,7 @@ public function testConvert()
     /**
      * @group unit
      */
-    public function testConvertWithNonDefaultOptions()
+    public function testConvertWithNonDefaultOptions(): void
     {
         $processor = new Convert('foo', 'integer');
         $processor->setIgnoreMissing(true);
@@ -62,7 +65,7 @@ public function testConvertWithNonDefaultOptions()
     /**
      * @group functional
      */
-    public function testConvertField()
+    public function testConvertField(): void
     {
         $append = new Convert('foo', 'float');
 
diff --git a/tests/Processor/DateIndexNameTest.php b/tests/Processor/DateIndexNameTest.php
index 1a3d6ec7c3..0fd08d2152 100644
--- a/tests/Processor/DateIndexNameTest.php
+++ b/tests/Processor/DateIndexNameTest.php
@@ -5,12 +5,15 @@
 use Elastica\Processor\DateIndexName;
 use Elastica\Test\BasePipeline as BasePipelineTest;
 
+/**
+ * @internal
+ */
 class DateIndexNameTest extends BasePipelineTest
 {
     /**
      * @group unit
      */
-    public function testDateIndexName()
+    public function testDateIndexName(): void
     {
         $processor = new DateIndexName('date1', 'M');
 
@@ -27,7 +30,7 @@ public function testDateIndexName()
     /**
      * @group unit
      */
-    public function testDateIndexNameWithNonDefaultOptions()
+    public function testDateIndexNameWithNonDefaultOptions(): void
     {
         $processor = new DateIndexName('date1', 'M');
         $processor->setTimezone('Europe/Rome');
diff --git a/tests/Processor/DateTest.php b/tests/Processor/DateTest.php
index 1afa009d4b..e59dc705cf 100644
--- a/tests/Processor/DateTest.php
+++ b/tests/Processor/DateTest.php
@@ -8,12 +8,15 @@
 use Elastica\ResultSet;
 use Elastica\Test\BasePipeline as BasePipelineTest;
 
+/**
+ * @internal
+ */
 class DateTest extends BasePipelineTest
 {
     /**
      * @group unit
      */
-    public function testDate()
+    public function testDate(): void
     {
         $processor = new Date('initial_date', ['dd/MM/yyyy hh:mm:ss']);
 
@@ -41,7 +44,7 @@ public function testDate()
     /**
      * @group unit
      */
-    public function testDateWithNonDefaultOptions()
+    public function testDateWithNonDefaultOptions(): void
     {
         $processor = new Date('initial_date', ['dd/MM/yyyy hh:mm:ss', 'ISO8601', 'UNIX', 'UNIX_MS']);
         $processor->setTargetField('timestamp');
@@ -64,7 +67,7 @@ public function testDateWithNonDefaultOptions()
     /**
      * @group functional
      */
-    public function testDateField()
+    public function testDateField(): void
     {
         $date = new Date('date_field', ['yyyy dd MM hh:mm:ss']);
         $date->setTargetField('date_parsed');
diff --git a/tests/Processor/DotExpanderTest.php b/tests/Processor/DotExpanderTest.php
index 72a94cb0da..0632a80267 100644
--- a/tests/Processor/DotExpanderTest.php
+++ b/tests/Processor/DotExpanderTest.php
@@ -8,12 +8,15 @@
 use Elastica\ResultSet;
 use Elastica\Test\BasePipeline as BasePipelineTest;
 
+/**
+ * @internal
+ */
 class DotExpanderTest extends BasePipelineTest
 {
     /**
      * @group unit
      */
-    public function testDotExpander()
+    public function testDotExpander(): void
     {
         $processor = new DotExpander('foo.bar');
 
@@ -29,7 +32,7 @@ public function testDotExpander()
     /**
      * @group functional
      */
-    public function testDotExpanderField()
+    public function testDotExpanderField(): void
     {
         $dotExpander = new DotExpander('foo.bar');
 
diff --git a/tests/Processor/FailTest.php b/tests/Processor/FailTest.php
index 04071795d5..3cb6732c42 100644
--- a/tests/Processor/FailTest.php
+++ b/tests/Processor/FailTest.php
@@ -8,12 +8,15 @@
 use Elastica\Processor\Json;
 use Elastica\Test\BasePipeline as BasePipelineTest;
 
+/**
+ * @internal
+ */
 class FailTest extends BasePipelineTest
 {
     /**
      * @group unit
      */
-    public function testFail()
+    public function testFail(): void
     {
         $processor = new Fail('This is a custom fail message for processor');
 
@@ -29,7 +32,7 @@ public function testFail()
     /**
      * @group functional
      */
-    public function testFailField()
+    public function testFailField(): void
     {
         $fail = new Fail('custom error fail message');
         $json = new Json('name');
diff --git a/tests/Processor/JoinTest.php b/tests/Processor/JoinTest.php
index a5cc1fadbd..056be2b157 100644
--- a/tests/Processor/JoinTest.php
+++ b/tests/Processor/JoinTest.php
@@ -8,12 +8,15 @@
 use Elastica\ResultSet;
 use Elastica\Test\BasePipeline as BasePipelineTest;
 
+/**
+ * @internal
+ */
 class JoinTest extends BasePipelineTest
 {
     /**
      * @group unit
      */
-    public function testJoin()
+    public function testJoin(): void
     {
         $processor = new Join('joined_array_field', '-');
 
@@ -30,7 +33,7 @@ public function testJoin()
     /**
      * @group functional
      */
-    public function testJoinField()
+    public function testJoinField(): void
     {
         $join = new Join('name', '-');
 
diff --git a/tests/Processor/JsonTest.php b/tests/Processor/JsonTest.php
index b82bdb1380..68a9bdd40f 100644
--- a/tests/Processor/JsonTest.php
+++ b/tests/Processor/JsonTest.php
@@ -8,12 +8,15 @@
 use Elastica\ResultSet;
 use Elastica\Test\BasePipeline as BasePipelineTest;
 
+/**
+ * @internal
+ */
 class JsonTest extends BasePipelineTest
 {
     /**
      * @group unit
      */
-    public function testJson()
+    public function testJson(): void
     {
         $processor = new Json('string_source');
 
@@ -29,7 +32,7 @@ public function testJson()
     /**
      * @group unit
      */
-    public function testJsonWithNonDefaultOptions()
+    public function testJsonWithNonDefaultOptions(): void
     {
         $processor = new Json('string_source');
         $processor->setTargetField('json_target');
@@ -49,7 +52,7 @@ public function testJsonWithNonDefaultOptions()
     /**
      * @group functional
      */
-    public function testJsonField()
+    public function testJsonField(): void
     {
         $json = new Json('name');
         $json->setTargetField('realname');
diff --git a/tests/Processor/KvTest.php b/tests/Processor/KvTest.php
index 67adb325e5..0450cb735b 100644
--- a/tests/Processor/KvTest.php
+++ b/tests/Processor/KvTest.php
@@ -5,12 +5,15 @@
 use Elastica\Processor\Kv;
 use Elastica\Test\BasePipeline as BasePipelineTest;
 
+/**
+ * @internal
+ */
 class KvTest extends BasePipelineTest
 {
     /**
      * @group unit
      */
-    public function testKv()
+    public function testKv(): void
     {
         $processor = new Kv('message', ' ', '=');
 
@@ -28,7 +31,7 @@ public function testKv()
     /**
      * @group unit
      */
-    public function testKvWithNonDefaultOptions()
+    public function testKvWithNonDefaultOptions(): void
     {
         $processor = new Kv('message', ' ', '=');
         $processor->setTargetField('target_field');
@@ -54,7 +57,7 @@ public function testKvWithNonDefaultOptions()
     /**
      * @group functional
      */
-    public function testKVIncludeExludeKeys()
+    public function testKVIncludeExludeKeys(): void
     {
         $kv = new Kv('field1', '&', '=');
         $kv->setExcludeKeys(['second']);
diff --git a/tests/Processor/LowercaseTest.php b/tests/Processor/LowercaseTest.php
index d49635a2c8..bf7f87bdc5 100644
--- a/tests/Processor/LowercaseTest.php
+++ b/tests/Processor/LowercaseTest.php
@@ -8,12 +8,15 @@
 use Elastica\ResultSet;
 use Elastica\Test\BasePipeline as BasePipelineTest;
 
+/**
+ * @internal
+ */
 class LowercaseTest extends BasePipelineTest
 {
     /**
      * @group unit
      */
-    public function testLowercase()
+    public function testLowercase(): void
     {
         $processor = new Lowercase('foo');
 
@@ -29,7 +32,7 @@ public function testLowercase()
     /**
      * @group functional
      */
-    public function testLowercaseField()
+    public function testLowercaseField(): void
     {
         $lcase = new Lowercase('name');
 
diff --git a/tests/Processor/RemoveTest.php b/tests/Processor/RemoveTest.php
index 117ca03909..af8e860e1b 100644
--- a/tests/Processor/RemoveTest.php
+++ b/tests/Processor/RemoveTest.php
@@ -8,12 +8,15 @@
 use Elastica\ResultSet;
 use Elastica\Test\BasePipeline as BasePipelineTest;
 
+/**
+ * @internal
+ */
 class RemoveTest extends BasePipelineTest
 {
     /**
      * @group unit
      */
-    public function testRemove()
+    public function testRemove(): void
     {
         $processor = new Remove('foo');
 
@@ -29,7 +32,7 @@ public function testRemove()
     /**
      * @group unit
      */
-    public function testRemoveArray()
+    public function testRemoveArray(): void
     {
         $processor = new Remove(['foo', 'bar']);
 
@@ -45,7 +48,7 @@ public function testRemoveArray()
     /**
      * @group functional
      */
-    public function testRemoveField()
+    public function testRemoveField(): void
     {
         $remove = new Remove(['es_version', 'package']);
 
diff --git a/tests/Processor/RenameTest.php b/tests/Processor/RenameTest.php
index f7a1cc1669..4a5c958927 100644
--- a/tests/Processor/RenameTest.php
+++ b/tests/Processor/RenameTest.php
@@ -8,12 +8,15 @@
 use Elastica\ResultSet;
 use Elastica\Test\BasePipeline as BasePipelineTest;
 
+/**
+ * @internal
+ */
 class RenameTest extends BasePipelineTest
 {
     /**
      * @group unit
      */
-    public function testRename()
+    public function testRename(): void
     {
         $processor = new Rename('foo', 'foobar');
 
@@ -30,7 +33,7 @@ public function testRename()
     /**
      * @group unit
      */
-    public function testRenameWithNonDefaultOptions()
+    public function testRenameWithNonDefaultOptions(): void
     {
         $processor = new Rename('foo', 'foobar');
         $processor->setIgnoreMissing(true);
@@ -49,7 +52,7 @@ public function testRenameWithNonDefaultOptions()
     /**
      * @group functional
      */
-    public function testRenameField()
+    public function testRenameField(): void
     {
         $rename = new Rename('package', 'packages');
 
diff --git a/tests/Processor/SetTest.php b/tests/Processor/SetTest.php
index 73200774e9..5ef2ff47c8 100644
--- a/tests/Processor/SetTest.php
+++ b/tests/Processor/SetTest.php
@@ -8,12 +8,15 @@
 use Elastica\ResultSet;
 use Elastica\Test\BasePipeline as BasePipelineTest;
 
+/**
+ * @internal
+ */
 class SetTest extends BasePipelineTest
 {
     /**
      * @group unit
      */
-    public function testSet()
+    public function testSet(): void
     {
         $processor = new Set('field1', 582.1);
 
@@ -30,7 +33,7 @@ public function testSet()
     /**
      * @group unit
      */
-    public function testSetWithNonDefaultOptions()
+    public function testSetWithNonDefaultOptions(): void
     {
         $processor = new Set('field1', 582.1);
         $processor->setOverride(false);
@@ -49,7 +52,7 @@ public function testSetWithNonDefaultOptions()
     /**
      * @group functional
      */
-    public function testSetField()
+    public function testSetField(): void
     {
         $set = new Set('package', 'Elastica');
 
diff --git a/tests/Processor/SortTest.php b/tests/Processor/SortTest.php
index 0166f29d1b..fd96c7ff05 100644
--- a/tests/Processor/SortTest.php
+++ b/tests/Processor/SortTest.php
@@ -8,12 +8,15 @@
 use Elastica\ResultSet;
 use Elastica\Test\BasePipeline as BasePipelineTest;
 
+/**
+ * @internal
+ */
 class SortTest extends BasePipelineTest
 {
     /**
      * @group unit
      */
-    public function testSort()
+    public function testSort(): void
     {
         $processor = new Sort('field_to_sort');
 
@@ -29,7 +32,7 @@ public function testSort()
     /**
      * @group unit
      */
-    public function testSortWithNonDefaultOptions()
+    public function testSortWithNonDefaultOptions(): void
     {
         $processor = new Sort('field_to_sort');
         $processor->setOrder('desc');
@@ -47,7 +50,7 @@ public function testSortWithNonDefaultOptions()
     /**
      * @group functional
      */
-    public function testSortField()
+    public function testSortField(): void
     {
         $sort = new Sort('name');
 
diff --git a/tests/Processor/SplitTest.php b/tests/Processor/SplitTest.php
index 9cc8e7cff7..ab9504b167 100644
--- a/tests/Processor/SplitTest.php
+++ b/tests/Processor/SplitTest.php
@@ -8,12 +8,15 @@
 use Elastica\ResultSet;
 use Elastica\Test\BasePipeline as BasePipelineTest;
 
+/**
+ * @internal
+ */
 class SplitTest extends BasePipelineTest
 {
     /**
      * @group unit
      */
-    public function testSplit()
+    public function testSplit(): void
     {
         $processor = new Split('joined_array_field', '-');
 
@@ -30,7 +33,7 @@ public function testSplit()
     /**
      * @group unit
      */
-    public function testSplitWithNonDefaultOptions()
+    public function testSplitWithNonDefaultOptions(): void
     {
         $processor = new Split('joined_array_field', '-');
         $processor->setIgnoreMissing(true);
@@ -49,7 +52,7 @@ public function testSplitWithNonDefaultOptions()
     /**
      * @group functional
      */
-    public function testSplitField()
+    public function testSplitField(): void
     {
         $split = new Split('name', '&');
 
diff --git a/tests/Processor/TrimTest.php b/tests/Processor/TrimTest.php
index 774d366a4a..ccc847edf1 100644
--- a/tests/Processor/TrimTest.php
+++ b/tests/Processor/TrimTest.php
@@ -8,12 +8,15 @@
 use Elastica\ResultSet;
 use Elastica\Test\BasePipeline as BasePipelineTest;
 
+/**
+ * @internal
+ */
 class TrimTest extends BasePipelineTest
 {
     /**
      * @group unit
      */
-    public function testTrim()
+    public function testTrim(): void
     {
         $processor = new Trim('foo');
 
@@ -29,7 +32,7 @@ public function testTrim()
     /**
      * @group functional
      */
-    public function testTrimField()
+    public function testTrimField(): void
     {
         $trim = new Trim('name');
 
diff --git a/tests/Processor/UppercaseTest.php b/tests/Processor/UppercaseTest.php
index 2f1d4c9a0f..5f377f7209 100644
--- a/tests/Processor/UppercaseTest.php
+++ b/tests/Processor/UppercaseTest.php
@@ -8,12 +8,15 @@
 use Elastica\ResultSet;
 use Elastica\Test\BasePipeline as BasePipelineTest;
 
+/**
+ * @internal
+ */
 class UppercaseTest extends BasePipelineTest
 {
     /**
      * @group unit
      */
-    public function testUppercase()
+    public function testUppercase(): void
     {
         $processor = new Uppercase('foo');
 
@@ -29,7 +32,7 @@ public function testUppercase()
     /**
      * @group functional
      */
-    public function testUppercaseField()
+    public function testUppercaseField(): void
     {
         $ucase = new Uppercase('name');
 
diff --git a/tests/Query/BoolQueryTest.php b/tests/Query/BoolQueryTest.php
index af43c666d3..54a87360a7 100644
--- a/tests/Query/BoolQueryTest.php
+++ b/tests/Query/BoolQueryTest.php
@@ -9,12 +9,15 @@
 use Elastica\Query\Term;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class BoolQueryTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $query = new BoolQuery();
 
@@ -65,7 +68,7 @@ public function testToArray()
      *
      * @group unit
      */
-    public function testToArrayStructure()
+    public function testToArrayStructure(): void
     {
         $boolQuery = new BoolQuery();
 
@@ -84,7 +87,7 @@ public function testToArrayStructure()
     /**
      * @group functional
      */
-    public function testSearch()
+    public function testSearch(): void
     {
         $client = $this->_getClient();
         $index = new Index($client, 'test');
@@ -137,7 +140,7 @@ public function testSearch()
     /**
      * @group functional
      */
-    public function testEmptyBoolQuery()
+    public function testEmptyBoolQuery(): void
     {
         $index = $this->_createIndex();
 
diff --git a/tests/Query/BoostingTest.php b/tests/Query/BoostingTest.php
index cd3d3a0fd3..f27fd508a2 100644
--- a/tests/Query/BoostingTest.php
+++ b/tests/Query/BoostingTest.php
@@ -6,12 +6,15 @@
 use Elastica\Query\Term;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class BoostingTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $keyword = 'vital';
         $negativeKeyword = 'Mercury';
@@ -36,7 +39,7 @@ public function testToArray()
     /**
      * @group unit
      */
-    public function testNegativeBoost()
+    public function testNegativeBoost(): void
     {
         $keyword = 'vital';
         $negativeKeyword = 'mercury';
diff --git a/tests/Query/CommonTest.php b/tests/Query/CommonTest.php
index bb8df9c331..cc6af0ad45 100644
--- a/tests/Query/CommonTest.php
+++ b/tests/Query/CommonTest.php
@@ -6,12 +6,15 @@
 use Elastica\Query\Common;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class CommonTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $query = new Common('body', 'test query', .001);
         $query->setLowFrequencyOperator(Common::OPERATOR_AND);
@@ -32,7 +35,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testQuery()
+    public function testQuery(): void
     {
         $index = $this->_createIndex();
 
@@ -64,7 +67,7 @@ public function testQuery()
     /**
      * @group unit
      */
-    public function testSetHighFrequencyOperator()
+    public function testSetHighFrequencyOperator(): void
     {
         $value = 'OPERATOR_TEST';
         $query = new Common('body', 'test query', .001);
@@ -76,7 +79,7 @@ public function testSetHighFrequencyOperator()
     /**
      * @group unit
      */
-    public function testSetBoost()
+    public function testSetBoost(): void
     {
         $value = .02;
         $query = new Common('body', 'test query', .001);
@@ -88,7 +91,7 @@ public function testSetBoost()
     /**
      * @group unit
      */
-    public function testSetAnalyzer()
+    public function testSetAnalyzer(): void
     {
         $analyzer = 'standard';
         $query = new Common('body', 'test query', .001);
diff --git a/tests/Query/ConstantScoreTest.php b/tests/Query/ConstantScoreTest.php
index 875028cf7f..bad3883434 100644
--- a/tests/Query/ConstantScoreTest.php
+++ b/tests/Query/ConstantScoreTest.php
@@ -6,12 +6,15 @@
 use Elastica\Query\Ids;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class ConstantScoreTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $query = new ConstantScore();
 
@@ -34,7 +37,7 @@ public function testToArray()
     /**
      * @group unit
      */
-    public function testConstruct()
+    public function testConstruct(): void
     {
         $filter = new Ids();
         $filter->setIds([1]);
@@ -53,7 +56,7 @@ public function testConstruct()
     /**
      * @group unit
      */
-    public function testConstructEmpty()
+    public function testConstructEmpty(): void
     {
         $query = new ConstantScore();
         $expectedArray = ['constant_score' => []];
diff --git a/tests/Query/DisMaxTest.php b/tests/Query/DisMaxTest.php
index b5079b158f..3e7e7f471c 100644
--- a/tests/Query/DisMaxTest.php
+++ b/tests/Query/DisMaxTest.php
@@ -8,12 +8,15 @@
 use Elastica\Query\QueryString;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class DisMaxTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $query = new DisMax();
 
@@ -53,7 +56,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testQuery()
+    public function testQuery(): void
     {
         $index = $this->_createIndex();
 
@@ -85,7 +88,7 @@ public function testQuery()
     /**
      * @group functional
      */
-    public function testQueryArray()
+    public function testQueryArray(): void
     {
         $index = $this->_createIndex();
 
@@ -99,8 +102,8 @@ public function testQueryArray()
         $index->refresh();
 
         $queryString1 = ['query_string' => [
-              'query' => 'Bade*',
-            ],
+            'query' => 'Bade*',
+        ],
         ];
 
         $queryString2 = ['query_string' => [
diff --git a/tests/Query/DistanceFeatureTest.php b/tests/Query/DistanceFeatureTest.php
index 243b9d61bc..a22e6736bb 100644
--- a/tests/Query/DistanceFeatureTest.php
+++ b/tests/Query/DistanceFeatureTest.php
@@ -5,12 +5,15 @@
 use Elastica\Query\DistanceFeature;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class DistanceFeatureTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArrayDate()
+    public function testToArrayDate(): void
     {
         $query = new DistanceFeature('field_date', 'now', '7d');
 
@@ -28,7 +31,7 @@ public function testToArrayDate()
     /**
      * @group unit
      */
-    public function testToArrayGeoPoint()
+    public function testToArrayGeoPoint(): void
     {
         $query = new DistanceFeature('field_geo_point', [-71.3, 41.15], '1000m');
 
@@ -46,7 +49,7 @@ public function testToArrayGeoPoint()
     /**
      * @group unit
      */
-    public function testSetBoost()
+    public function testSetBoost(): void
     {
         $query = new DistanceFeature('field_date', 'now', '7d');
         $query->setBoost($value = 2.0);
diff --git a/tests/Query/EscapeStringTest.php b/tests/Query/EscapeStringTest.php
index 50256986a9..2d16bee378 100644
--- a/tests/Query/EscapeStringTest.php
+++ b/tests/Query/EscapeStringTest.php
@@ -7,18 +7,23 @@
 use Elastica\Test\Base as BaseTest;
 use Elastica\Util;
 
+/**
+ * @internal
+ */
 class EscapeStringTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testSearch()
+    public function testSearch(): void
     {
         $index = $this->_createIndex();
         $index->getSettings()->setNumberOfReplicas(0);
 
-        $doc = new Document(1, [
-            'email' => 'test@test.com', 'username' => 'test 7/6 123', 'test' => ['2', '3', '5'], ]
+        $doc = new Document(
+            1,
+            [
+                'email' => 'test@test.com', 'username' => 'test 7/6 123', 'test' => ['2', '3', '5'], ]
         );
         $index->addDocument($doc);
 
diff --git a/tests/Query/ExistsTest.php b/tests/Query/ExistsTest.php
index 8445f65b14..42e2ed8d97 100644
--- a/tests/Query/ExistsTest.php
+++ b/tests/Query/ExistsTest.php
@@ -5,12 +5,15 @@
 use Elastica\Query\Exists;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class ExistsTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $field = 'test';
         $query = new Exists($field);
@@ -22,7 +25,7 @@ public function testToArray()
     /**
      * @group unit
      */
-    public function testSetField()
+    public function testSetField(): void
     {
         $field = 'test';
         $query = new Exists($field);
diff --git a/tests/Query/FunctionScoreTest.php b/tests/Query/FunctionScoreTest.php
index be046ee16a..74cc393912 100644
--- a/tests/Query/FunctionScoreTest.php
+++ b/tests/Query/FunctionScoreTest.php
@@ -10,44 +10,17 @@
 use Elastica\Script\Script;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class FunctionScoreTest extends BaseTest
 {
     protected $locationOrigin = '32.804654, -117.242594';
 
-    protected function _getIndexForTest()
-    {
-        $index = $this->_createIndex();
-        $index->setMapping(new Mapping([
-            'name' => ['type' => 'text', 'index' => 'false'],
-            'location' => ['type' => 'geo_point'],
-            'price' => ['type' => 'float'],
-            'popularity' => ['type' => 'integer'],
-        ]));
-
-        $index->addDocuments([
-            new Document(1, [
-                'name' => "Mr. Frostie's",
-                'location' => [['lat' => 32.799605, 'lon' => -117.243027], ['lat' => 32.792744, 'lon' => -117.2387341]],
-                'price' => 4.5,
-                'popularity' => null,
-            ]),
-            new Document(2, [
-                'name' => "Miller's Field",
-                'location' => ['lat' => 32.795964, 'lon' => -117.255028],
-                'price' => 9.5,
-                'popularity' => 1,
-            ]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $priceOrigin = 0;
         $locationScale = '2mi';
@@ -86,7 +59,7 @@ public function testToArray()
     /**
      * @group unit
      */
-    public function testDecayWeight()
+    public function testDecayWeight(): void
     {
         $priceOrigin = 0;
         $locationScale = '2mi';
@@ -149,7 +122,7 @@ public function testDecayWeight()
     /**
      * @group functional
      */
-    public function testGauss()
+    public function testGauss(): void
     {
         $query = new FunctionScore();
         $query->addDecayFunction(FunctionScore::DECAY_GAUSS, 'location', $this->locationOrigin, '4mi');
@@ -165,7 +138,7 @@ public function testGauss()
     /**
      * @group functional
      */
-    public function testGaussMultiValue()
+    public function testGaussMultiValue(): void
     {
         $query = new FunctionScore();
         $query->addDecayFunction(
@@ -190,7 +163,7 @@ public function testGaussMultiValue()
     /**
      * @group unit
      */
-    public function testAddWeightFunction()
+    public function testAddWeightFunction(): void
     {
         $filter = new Term(['price' => 4.5]);
         $query = new FunctionScore();
@@ -206,7 +179,7 @@ public function testAddWeightFunction()
     /**
      * @group unit
      */
-    public function testLegacyFilterAddWeightFunction()
+    public function testLegacyFilterAddWeightFunction(): void
     {
         $query = new FunctionScore();
         $filter = new Term(['price' => 4.5]);
@@ -222,7 +195,7 @@ public function testLegacyFilterAddWeightFunction()
     /**
      * @group functional
      */
-    public function testWeight()
+    public function testWeight(): void
     {
         $filter = new Term(['price' => 4.5]);
         $query = new FunctionScore();
@@ -256,7 +229,7 @@ public function testWeight()
     /**
      * @group functional
      */
-    public function testWeightWithLegacyFilter()
+    public function testWeightWithLegacyFilter(): void
     {
         $filter = new Term(['price' => 4.5]);
         $query = new FunctionScore();
@@ -290,7 +263,7 @@ public function testWeightWithLegacyFilter()
     /**
      * @group functional
      */
-    public function testRandomScore()
+    public function testRandomScore(): void
     {
         $filter = new Term(['price' => 4.5]);
         $query = new FunctionScore();
@@ -328,7 +301,7 @@ public function testRandomScore()
     /**
      * @group functional
      */
-    public function testRandomScoreWithLegacyFilter()
+    public function testRandomScoreWithLegacyFilter(): void
     {
         $filter = new Term(['price' => 4.5]);
         $query = new FunctionScore();
@@ -366,7 +339,7 @@ public function testRandomScoreWithLegacyFilter()
     /**
      * @group unit
      */
-    public function testRandomScoreWeight()
+    public function testRandomScoreWeight(): void
     {
         $filter = new Term(['price' => 4.5]);
         $query = new FunctionScore();
@@ -397,7 +370,7 @@ public function testRandomScoreWeight()
     /**
      * @group unit
      */
-    public function testRandomScoreWeightWithLegacyFilter()
+    public function testRandomScoreWeightWithLegacyFilter(): void
     {
         $filter = new Term(['price' => 4.5]);
         $query = new FunctionScore();
@@ -428,7 +401,7 @@ public function testRandomScoreWeightWithLegacyFilter()
     /**
      * @group functional
      */
-    public function testRandomScoreWithoutSeed()
+    public function testRandomScoreWithoutSeed(): void
     {
         $query = new FunctionScore();
         $query->setRandomScore();
@@ -441,7 +414,7 @@ public function testRandomScoreWithoutSeed()
     /**
      * @group functional
      */
-    public function testRandomScoreWithoutField()
+    public function testRandomScoreWithoutField(): void
     {
         $filter = new Term(['price' => 4.5]);
         $query = new FunctionScore();
@@ -478,7 +451,7 @@ public function testRandomScoreWithoutField()
     /**
      * @group functional
      */
-    public function testScriptScore()
+    public function testScriptScore(): void
     {
         $scriptString = "_score * doc['price'].value";
         $script = new Script($scriptString, null, Script::LANG_PAINLESS);
@@ -512,7 +485,7 @@ public function testScriptScore()
     /**
      * @group functional
      */
-    public function testSetMinScore()
+    public function testSetMinScore(): void
     {
         $this->_checkVersion('1.5');
 
@@ -549,7 +522,7 @@ public function testSetMinScore()
     /**
      * @group functional
      */
-    public function testFieldValueFactor()
+    public function testFieldValueFactor(): void
     {
         $this->_checkVersion('1.6');
 
@@ -579,4 +552,34 @@ public function testFieldValueFactor()
         $this->assertCount(2, $results);
         $this->assertEquals(2, $results[0]->getId());
     }
+
+    protected function _getIndexForTest()
+    {
+        $index = $this->_createIndex();
+        $index->setMapping(new Mapping([
+            'name' => ['type' => 'text', 'index' => 'false'],
+            'location' => ['type' => 'geo_point'],
+            'price' => ['type' => 'float'],
+            'popularity' => ['type' => 'integer'],
+        ]));
+
+        $index->addDocuments([
+            new Document(1, [
+                'name' => "Mr. Frostie's",
+                'location' => [['lat' => 32.799605, 'lon' => -117.243027], ['lat' => 32.792744, 'lon' => -117.2387341]],
+                'price' => 4.5,
+                'popularity' => null,
+            ]),
+            new Document(2, [
+                'name' => "Miller's Field",
+                'location' => ['lat' => 32.795964, 'lon' => -117.255028],
+                'price' => 9.5,
+                'popularity' => 1,
+            ]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Query/FuzzyTest.php b/tests/Query/FuzzyTest.php
index aac798358d..d5eab6e757 100644
--- a/tests/Query/FuzzyTest.php
+++ b/tests/Query/FuzzyTest.php
@@ -7,12 +7,15 @@
 use Elastica\Query\Fuzzy;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class FuzzyTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testAddField()
+    public function testAddField(): void
     {
         $fuzzy = new Fuzzy();
         $fuzzy->setField('user', 'Nicolas');
@@ -28,7 +31,7 @@ public function testAddField()
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $fuzzy = new Fuzzy();
 
@@ -71,7 +74,7 @@ public function testToArray()
     /**
      * @group unit
      */
-    public function testNeedSetFieldBeforeOption()
+    public function testNeedSetFieldBeforeOption(): void
     {
         $fuzzy = new Fuzzy();
         $this->expectException(InvalidException::class);
@@ -82,7 +85,7 @@ public function testNeedSetFieldBeforeOption()
     /**
      * @group functional
      */
-    public function testQuery()
+    public function testQuery(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('test');
@@ -110,7 +113,7 @@ public function testQuery()
     /**
      * @group unit
      */
-    public function testResetSingleField()
+    public function testResetSingleField(): void
     {
         $fuzzy = new Fuzzy();
         $fuzzy->setField('name', 'value');
@@ -128,7 +131,7 @@ public function testResetSingleField()
     /**
      * @group unit
      */
-    public function testOnlySetSingleField()
+    public function testOnlySetSingleField(): void
     {
         $fuzzy = new Fuzzy();
         $fuzzy->setField('name', 'value');
diff --git a/tests/Query/GeoBoundingBoxTest.php b/tests/Query/GeoBoundingBoxTest.php
index c969623110..c53dee8343 100644
--- a/tests/Query/GeoBoundingBoxTest.php
+++ b/tests/Query/GeoBoundingBoxTest.php
@@ -5,12 +5,15 @@
 use Elastica\Query\GeoBoundingBox;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class GeoBoundingBoxTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testAddCoordinates()
+    public function testAddCoordinates(): void
     {
         $key = 'pin.location';
         $coords = ['40.73, -74.1', '40.01, -71.12'];
@@ -27,7 +30,7 @@ public function testAddCoordinates()
     /**
      * @group unit
      */
-    public function testAddCoordinatesInvalidException()
+    public function testAddCoordinatesInvalidException(): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
 
@@ -37,7 +40,7 @@ public function testAddCoordinatesInvalidException()
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $key = 'pin.location';
         $coords = ['40.73, -74.1', '40.01, -71.12'];
diff --git a/tests/Query/GeoDistanceTest.php b/tests/Query/GeoDistanceTest.php
index e29c9b2ceb..8ee57cb2ba 100644
--- a/tests/Query/GeoDistanceTest.php
+++ b/tests/Query/GeoDistanceTest.php
@@ -8,12 +8,15 @@
 use Elastica\Query\GeoDistance;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class GeoDistanceTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testGeoPoint()
+    public function testGeoPoint(): void
     {
         $index = $this->_createIndex();
         $index->setMapping(new Mapping(['point' => ['type' => 'geo_point']]));
@@ -49,7 +52,7 @@ public function testGeoPoint()
     /**
      * @group unit
      */
-    public function testConstructLatlon()
+    public function testConstructLatlon(): void
     {
         $key = 'location';
         $location = [
@@ -75,7 +78,7 @@ public function testConstructLatlon()
     /**
      * @group unit
      */
-    public function testConstructGeohash()
+    public function testConstructGeohash(): void
     {
         $key = 'location';
         $location = 'u09tvqx';
@@ -98,7 +101,7 @@ public function testConstructGeohash()
     /**
      * @group unit
      */
-    public function testSetDistanceType()
+    public function testSetDistanceType(): void
     {
         $query = new GeoDistance('location', ['lat' => 48.86, 'lon' => 2.35], '10km');
         $distanceType = GeoDistance::DISTANCE_TYPE_ARC;
diff --git a/tests/Query/GeoPolygonTest.php b/tests/Query/GeoPolygonTest.php
index bfdaa7b9a6..403ade792e 100644
--- a/tests/Query/GeoPolygonTest.php
+++ b/tests/Query/GeoPolygonTest.php
@@ -9,12 +9,15 @@
 use Elastica\Query\MatchAll;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class GeoPolygonTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testGeoPoint()
+    public function testGeoPoint(): void
     {
         $index = $this->_createIndex();
 
@@ -22,7 +25,8 @@ public function testGeoPoint()
         $index->setMapping(new Mapping(['location' => ['type' => 'geo_point']]));
 
         // Add doc 1
-        $doc1 = new Document(1,
+        $doc1 = new Document(
+            1,
             [
                 'name' => 'ruflin',
             ]
@@ -32,7 +36,8 @@ public function testGeoPoint()
         $index->addDocument($doc1);
 
         // Add doc 2
-        $doc2 = new Document(2,
+        $doc2 = new Document(
+            2,
             [
                 'name' => 'ruflin',
             ]
diff --git a/tests/Query/GeoShapePreIndexedTest.php b/tests/Query/GeoShapePreIndexedTest.php
index d2ffcad9af..5363c3f4bc 100644
--- a/tests/Query/GeoShapePreIndexedTest.php
+++ b/tests/Query/GeoShapePreIndexedTest.php
@@ -9,12 +9,15 @@
 use Elastica\Query\GeoShapePreIndexed;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class GeoShapePreIndexedTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testSearch()
+    public function testSearch(): void
     {
         $index = $this->_createIndex();
         $indexName = $index->getName();
@@ -40,7 +43,10 @@ public function testSearch()
         $index->refresh();
 
         $gsp = new GeoShapePreIndexed(
-            'location', '2', $indexName, 'location'
+            'location',
+            '2',
+            $indexName,
+            'location'
         );
 
         $query = new BoolQuery();
@@ -55,10 +61,13 @@ public function testSearch()
     /**
      * @group unit
      */
-    public function testConstruct()
+    public function testConstruct(): void
     {
         $gsp = new GeoShapePreIndexed(
-            'search_field', '1', 'index', 'indexed_field'
+            'search_field',
+            '1',
+            'index',
+            'indexed_field'
         );
 
         $expected = [
@@ -80,7 +89,7 @@ public function testConstruct()
     /**
      * @group unit
      */
-    public function testSetRelation()
+    public function testSetRelation(): void
     {
         $gsp = new GeoShapePreIndexed('location', '1', 'indexName', 'location');
 
diff --git a/tests/Query/GeoShapeProvidedTest.php b/tests/Query/GeoShapeProvidedTest.php
index ec4340cc8b..3f73fad270 100644
--- a/tests/Query/GeoShapeProvidedTest.php
+++ b/tests/Query/GeoShapeProvidedTest.php
@@ -9,12 +9,15 @@
 use Elastica\Query\GeoShapeProvided;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class GeoShapeProvidedTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testSearch()
+    public function testSearch(): void
     {
         $index = $this->_createIndex();
         $mapping = new Mapping([
@@ -58,7 +61,7 @@ public function testSearch()
     /**
      * @group unit
      */
-    public function testConstructEnvelope()
+    public function testConstructEnvelope(): void
     {
         $envelope = [
             [25.0, 75.0],
@@ -84,7 +87,7 @@ public function testConstructEnvelope()
     /**
      * @group unit
      */
-    public function testConstructPolygon()
+    public function testConstructPolygon(): void
     {
         $polygon = [[102.0, 2.0], [103.0, 2.0], [103.0, 3.0], [103.0, 3.0], [102.0, 2.0]];
         $gsp = new GeoShapeProvided('location', $polygon, GeoShapeProvided::TYPE_POLYGON);
@@ -107,7 +110,7 @@ public function testConstructPolygon()
     /**
      * @group unit
      */
-    public function testSetRelation()
+    public function testSetRelation(): void
     {
         $gsp = new GeoShapeProvided('location', [[25.0, 75.0], [75.0, 25.0]]);
 
diff --git a/tests/Query/HasChildTest.php b/tests/Query/HasChildTest.php
index c234eee32e..85868fd9db 100644
--- a/tests/Query/HasChildTest.php
+++ b/tests/Query/HasChildTest.php
@@ -8,12 +8,15 @@
 use Elastica\Search;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class HasChildTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $q = new MatchAll();
 
@@ -34,7 +37,7 @@ public function testToArray()
     /**
      * @group unit
      */
-    public function testSetScope()
+    public function testSetScope(): void
     {
         $q = new MatchAll();
 
@@ -59,7 +62,7 @@ public function testSetScope()
     /**
      * @group functional
      */
-    public function testHasChildren()
+    public function testHasChildren(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('testhaschild');
diff --git a/tests/Query/HasParentTest.php b/tests/Query/HasParentTest.php
index c3e7534eae..16563e8d48 100644
--- a/tests/Query/HasParentTest.php
+++ b/tests/Query/HasParentTest.php
@@ -8,12 +8,15 @@
 use Elastica\Search;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class HasParentTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $q = new MatchAll();
 
@@ -34,7 +37,7 @@ public function testToArray()
     /**
      * @group unit
      */
-    public function testSetScope()
+    public function testSetScope(): void
     {
         $q = new MatchAll();
 
@@ -59,7 +62,7 @@ public function testSetScope()
     /**
      * @group functional
      */
-    public function testHasParent()
+    public function testHasParent(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('testhasparentjoin');
diff --git a/tests/Query/HighlightTest.php b/tests/Query/HighlightTest.php
index ebde4bfab2..17a847a987 100644
--- a/tests/Query/HighlightTest.php
+++ b/tests/Query/HighlightTest.php
@@ -7,12 +7,15 @@
 use Elastica\Query\MatchPhrase;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class HighlightTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testHightlightSearch()
+    public function testHightlightSearch(): void
     {
         $index = $this->_createIndex();
 
diff --git a/tests/Query/IdsTest.php b/tests/Query/IdsTest.php
index b72e1999ab..c0c7b01112 100644
--- a/tests/Query/IdsTest.php
+++ b/tests/Query/IdsTest.php
@@ -8,12 +8,15 @@
 use Elastica\Query\Type;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class IdsTest extends BaseTest
 {
     /** @var Index */
     protected $index;
 
-    protected function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
 
@@ -29,7 +32,7 @@ protected function setUp()
     /**
      * @group functional
      */
-    public function testSetIdsSearchSingle()
+    public function testSetIdsSearchSingle(): void
     {
         $query = new Ids();
         $query->setIds('1');
@@ -42,7 +45,7 @@ public function testSetIdsSearchSingle()
     /**
      * @group functional
      */
-    public function testSetIdsSearchArray()
+    public function testSetIdsSearchArray(): void
     {
         $query = new Ids();
         $query->setIds(['1', '2']);
@@ -55,7 +58,7 @@ public function testSetIdsSearchArray()
     /**
      * @group functional
      */
-    public function testAddIdsSearchSingle()
+    public function testAddIdsSearchSingle(): void
     {
         $query = new Ids();
         $query->addId('3');
@@ -68,7 +71,7 @@ public function testAddIdsSearchSingle()
     /**
      * @group functional
      */
-    public function testComboIdsSearchArray()
+    public function testComboIdsSearchArray(): void
     {
         $query = new Ids();
 
@@ -83,7 +86,7 @@ public function testComboIdsSearchArray()
     /**
      * @group functional
      */
-    public function testSetTypeSingleSearchSingle()
+    public function testSetTypeSingleSearchSingle(): void
     {
         $query = new Ids();
         $query->setIds('1');
@@ -95,7 +98,7 @@ public function testSetTypeSingleSearchSingle()
     /**
      * @group functional
      */
-    public function testSetTypeSingleSearchArray()
+    public function testSetTypeSingleSearchArray(): void
     {
         $query = new Ids();
         $query->setIds(['1', '2']);
@@ -108,7 +111,7 @@ public function testSetTypeSingleSearchArray()
     /**
      * @group functional
      */
-    public function testSetTypeSingleSearchSingleDocInOtherType()
+    public function testSetTypeSingleSearchSingleDocInOtherType(): void
     {
         $query = new Ids();
 
@@ -124,7 +127,7 @@ public function testSetTypeSingleSearchSingleDocInOtherType()
     /**
      * @group functional
      */
-    public function testSetTypeSingleSearchArrayDocInOtherType()
+    public function testSetTypeSingleSearchArrayDocInOtherType(): void
     {
         $query = new Ids();
 
diff --git a/tests/Query/InnerHitsTest.php b/tests/Query/InnerHitsTest.php
index 26bbe31dd0..647f875832 100644
--- a/tests/Query/InnerHitsTest.php
+++ b/tests/Query/InnerHitsTest.php
@@ -13,165 +13,15 @@
 use Elastica\Script\ScriptFields;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class InnerHitsTest extends BaseTest
 {
-    private function _getIndexForNestedTest()
-    {
-        $index = $this->_createIndex();
-        $index->setMapping(new Mapping([
-            'users' => [
-                'type' => 'nested',
-                'properties' => [
-                    'name' => ['type' => 'text', 'fielddata' => true],
-                ],
-            ],
-            'title' => ['type' => 'text'],
-            'last_activity_date' => ['type' => 'date'],
-        ]));
-
-        $index->addDocuments([
-            $index->createDocument(1, [
-                'users' => [
-                    ['name' => 'John Smith', 'last_activity_date' => '2015-01-05'],
-                    ['name' => 'Conan', 'last_activity_date' => '2015-01-05'],
-                ],
-                'last_activity_date' => '2015-01-05',
-                'title' => 'Question about linux #1',
-            ]),
-            $index->createDocument(2, [
-                'users' => [
-                    ['name' => 'John Doe', 'last_activity_date' => '2015-01-05'],
-                    ['name' => 'Simon', 'last_activity_date' => '2015-01-05'],
-                ],
-                'last_activity_date' => '2014-12-23',
-                'title' => 'Question about linux #2',
-            ]),
-            $index->createDocument(3, [
-                'users' => [
-                    ['name' => 'Simon', 'last_activity_date' => '2015-01-05'],
-                    ['name' => 'Garfunkel', 'last_activity_date' => '2015-01-05'],
-                ],
-                'last_activity_date' => '2015-01-05',
-                'title' => 'Question about windows #1',
-            ]),
-            $index->createDocument(4, [
-                'users' => [
-                    ['name' => 'Einstein'],
-                    ['name' => 'Newton'],
-                    ['name' => 'Maxwell'],
-                ],
-                'last_activity_date' => '2014-12-23',
-                'title' => 'Question about windows #2',
-            ]),
-            $index->createDocument(5, [
-                'users' => [
-                    ['name' => 'Faraday'],
-                    ['name' => 'Leibniz'],
-                    ['name' => 'Descartes'],
-                ],
-                'last_activity_date' => '2014-12-23',
-                'title' => 'Question about osx',
-            ]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
-    private function _getIndexForParentChildrenTest()
-    {
-        $index = $this->_createIndex();
-        $mappingQuestion = new Mapping();
-        $mappingQuestion->setProperties([
-            'title' => ['type' => 'text'],
-            'answer' => ['type' => 'text', 'fielddata' => true],
-            'last_activity_date' => ['type' => 'date'],
-            'my_join_field' => [
-                'type' => 'join',
-                'relations' => [
-                    'questions' => 'answers',
-                ],
-            ],
-        ]);
-
-        $index->setMapping($mappingQuestion);
-        $index->addDocuments([
-            $index->createDocument(1, [
-                'last_activity_date' => '2015-01-05',
-                'title' => 'Question about linux #1',
-                'my_join_field' => [
-                    'name' => 'questions',
-                ],
-            ]),
-            $index->createDocument(2, [
-                'last_activity_date' => '2014-12-23',
-                'title' => 'Question about linux #2',
-                'my_join_field' => [
-                    'name' => 'questions',
-                ],
-            ]),
-            $index->createDocument(3, [
-                'last_activity_date' => '2015-01-05',
-                'title' => 'Question about windows #1',
-                'my_join_field' => [
-                    'name' => 'questions',
-                ],
-            ]),
-            $index->createDocument(4, [
-                'last_activity_date' => '2014-12-23',
-                'title' => 'Question about windows #2',
-                'my_join_field' => [
-                    'name' => 'questions',
-                ],
-            ]),
-            $index->createDocument(5, [
-                'last_activity_date' => '2014-12-23',
-                'title' => 'Question about osx',
-                'my_join_field' => [
-                    'name' => 'questions',
-                ],
-            ]),
-        ]);
-
-        $doc1 = $index->createDocument(6, [
-            'answer' => 'linux is cool',
-            'last_activity_date' => '2016-01-05',
-            'my_join_field' => [
-                'name' => 'answers',
-                'parent' => 1,
-            ],
-        ]);
-
-        $doc2 = $index->createDocument(7, [
-            'answer' => 'linux is bad',
-            'last_activity_date' => '2005-01-05',
-            'my_join_field' => [
-                'name' => 'answers',
-                'parent' => 1,
-            ],
-        ]);
-
-        $doc3 = $index->createDocument(8, [
-            'answer' => 'windows was cool',
-            'last_activity_date' => '2005-01-05',
-            'my_join_field' => [
-                'name' => 'answers',
-                'parent' => 2,
-            ],
-        ]);
-
-        $this->_getClient()->addDocuments([$doc1, $doc2, $doc3], ['routing' => 1]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group unit
      */
-    public function testSetSize()
+    public function testSetSize(): void
     {
         $innerHits = new InnerHits();
         $returnValue = $innerHits->setSize(12);
@@ -182,7 +32,7 @@ public function testSetSize()
     /**
      * @group unit
      */
-    public function testSetFrom()
+    public function testSetFrom(): void
     {
         $innerHits = new InnerHits();
         $returnValue = $innerHits->setFrom(12);
@@ -193,7 +43,7 @@ public function testSetFrom()
     /**
      * @group unit
      */
-    public function testSetSort()
+    public function testSetSort(): void
     {
         $sort = ['last_activity_date' => ['order' => 'desc']];
         $innerHits = new InnerHits();
@@ -205,7 +55,7 @@ public function testSetSort()
     /**
      * @group unit
      */
-    public function testSetSource()
+    public function testSetSource(): void
     {
         $fields = ['title', 'tags'];
         $innerHits = new InnerHits();
@@ -217,7 +67,7 @@ public function testSetSource()
     /**
      * @group unit
      */
-    public function testSetVersion()
+    public function testSetVersion(): void
     {
         $innerHits = new InnerHits();
         $returnValue = $innerHits->setVersion(true);
@@ -231,7 +81,7 @@ public function testSetVersion()
     /**
      * @group unit
      */
-    public function testSetExplain()
+    public function testSetExplain(): void
     {
         $innerHits = new InnerHits();
         $returnValue = $innerHits->setExplain(true);
@@ -245,7 +95,7 @@ public function testSetExplain()
     /**
      * @group unit
      */
-    public function testSetHighlight()
+    public function testSetHighlight(): void
     {
         $highlight = [
             'fields' => [
@@ -261,7 +111,7 @@ public function testSetHighlight()
     /**
      * @group unit
      */
-    public function testSetFieldDataFields()
+    public function testSetFieldDataFields(): void
     {
         $fields = ['title', 'tags'];
         $innerHits = new InnerHits();
@@ -273,7 +123,7 @@ public function testSetFieldDataFields()
     /**
      * @group unit
      */
-    public function testSetScriptFields()
+    public function testSetScriptFields(): void
     {
         $script = new Script('1 + 2');
         $scriptFields = new ScriptFields(['three' => $script]);
@@ -287,7 +137,7 @@ public function testSetScriptFields()
     /**
      * @group unit
      */
-    public function testAddScriptField()
+    public function testAddScriptField(): void
     {
         $script = new Script('2+3');
         $innerHits = new InnerHits();
@@ -296,27 +146,10 @@ public function testAddScriptField()
         $this->assertInstanceOf(InnerHits::class, $returnValue);
     }
 
-    private function getNestedQuery(AbstractQuery $query, InnerHits $innerHits)
-    {
-        $nested = (new Nested())
-            ->setInnerHits($innerHits)
-            ->setPath('users')
-            ->setQuery($query);
-
-        return $this->_getIndexForNestedTest()->search($nested);
-    }
-
-    private function getParentChildQuery(AbstractQuery $query, InnerHits $innerHits)
-    {
-        $child = (new HasChild($query, 'answers'))->setInnerHits($innerHits);
-
-        return $this->_getIndexForParentChildrenTest()->search($child);
-    }
-
     /**
      * @group functional
      */
-    public function testInnerHitsNested()
+    public function testInnerHitsNested(): void
     {
         $queryString = new SimpleQueryString('windows newton', ['title', 'users.name']);
         $innerHits = new InnerHits();
@@ -333,7 +166,7 @@ public function testInnerHitsNested()
     /**
      * @group functional
      */
-    public function testInnerHitsParentChildren()
+    public function testInnerHitsParentChildren(): void
     {
         $queryString = new SimpleQueryString('linux cool');
         $innerHits = new InnerHits();
@@ -357,7 +190,7 @@ public function testInnerHitsParentChildren()
     /**
      * @group functional
      */
-    public function testInnerHitsLimitedSource()
+    public function testInnerHitsLimitedSource(): void
     {
         $this->markTestSkipped('Source filtering on inner hits is bugged. See https://github.com/elastic/elasticsearch/issues/21312');
 
@@ -378,7 +211,7 @@ public function testInnerHitsLimitedSource()
     /**
      * @group functional
      */
-    public function testInnerHitsWithOffset()
+    public function testInnerHitsWithOffset(): void
     {
         $queryString = new SimpleQueryString('linux cool');
         $innerHits = new InnerHits();
@@ -398,7 +231,7 @@ public function testInnerHitsWithOffset()
     /**
      * @group functional
      */
-    public function testInnerHitsWithSort()
+    public function testInnerHitsWithSort(): void
     {
         $queryString = new SimpleQueryString('linux cool');
         $innerHits = new InnerHits();
@@ -423,7 +256,7 @@ public function testInnerHitsWithSort()
     /**
      * @group functional
      */
-    public function testInnerHitsWithExplain()
+    public function testInnerHitsWithExplain(): void
     {
         $matchAll = new MatchAll();
         $innerHits = new InnerHits();
@@ -442,7 +275,7 @@ public function testInnerHitsWithExplain()
     /**
      * @group functional
      */
-    public function testInnerHitsWithVersion()
+    public function testInnerHitsWithVersion(): void
     {
         $matchAll = new MatchAll();
         $innerHits = new InnerHits();
@@ -461,7 +294,7 @@ public function testInnerHitsWithVersion()
     /**
      * @group functional
      */
-    public function testInnerHitsWithScriptFields()
+    public function testInnerHitsWithScriptFields(): void
     {
         $matchAll = new MatchAll();
         $innerHits = new InnerHits();
@@ -485,7 +318,7 @@ public function testInnerHitsWithScriptFields()
     /**
      * @group functional
      */
-    public function testInnerHitsWithHighlight()
+    public function testInnerHitsWithHighlight(): void
     {
         $queryString = new SimpleQueryString('question simon', ['title', 'users.name']);
         $innerHits = new InnerHits();
@@ -505,7 +338,7 @@ public function testInnerHitsWithHighlight()
     /**
      * @group functional
      */
-    public function testInnerHitsWithFieldData()
+    public function testInnerHitsWithFieldData(): void
     {
         $queryString = new SimpleQueryString('question simon', ['title', 'users.name']);
         $innerHits = new InnerHits();
@@ -523,4 +356,175 @@ public function testInnerHitsWithFieldData()
             }
         }
     }
+
+    private function _getIndexForNestedTest()
+    {
+        $index = $this->_createIndex();
+        $index->setMapping(new Mapping([
+            'users' => [
+                'type' => 'nested',
+                'properties' => [
+                    'name' => ['type' => 'text', 'fielddata' => true],
+                ],
+            ],
+            'title' => ['type' => 'text'],
+            'last_activity_date' => ['type' => 'date'],
+        ]));
+
+        $index->addDocuments([
+            $index->createDocument(1, [
+                'users' => [
+                    ['name' => 'John Smith', 'last_activity_date' => '2015-01-05'],
+                    ['name' => 'Conan', 'last_activity_date' => '2015-01-05'],
+                ],
+                'last_activity_date' => '2015-01-05',
+                'title' => 'Question about linux #1',
+            ]),
+            $index->createDocument(2, [
+                'users' => [
+                    ['name' => 'John Doe', 'last_activity_date' => '2015-01-05'],
+                    ['name' => 'Simon', 'last_activity_date' => '2015-01-05'],
+                ],
+                'last_activity_date' => '2014-12-23',
+                'title' => 'Question about linux #2',
+            ]),
+            $index->createDocument(3, [
+                'users' => [
+                    ['name' => 'Simon', 'last_activity_date' => '2015-01-05'],
+                    ['name' => 'Garfunkel', 'last_activity_date' => '2015-01-05'],
+                ],
+                'last_activity_date' => '2015-01-05',
+                'title' => 'Question about windows #1',
+            ]),
+            $index->createDocument(4, [
+                'users' => [
+                    ['name' => 'Einstein'],
+                    ['name' => 'Newton'],
+                    ['name' => 'Maxwell'],
+                ],
+                'last_activity_date' => '2014-12-23',
+                'title' => 'Question about windows #2',
+            ]),
+            $index->createDocument(5, [
+                'users' => [
+                    ['name' => 'Faraday'],
+                    ['name' => 'Leibniz'],
+                    ['name' => 'Descartes'],
+                ],
+                'last_activity_date' => '2014-12-23',
+                'title' => 'Question about osx',
+            ]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
+
+    private function _getIndexForParentChildrenTest()
+    {
+        $index = $this->_createIndex();
+        $mappingQuestion = new Mapping();
+        $mappingQuestion->setProperties([
+            'title' => ['type' => 'text'],
+            'answer' => ['type' => 'text', 'fielddata' => true],
+            'last_activity_date' => ['type' => 'date'],
+            'my_join_field' => [
+                'type' => 'join',
+                'relations' => [
+                    'questions' => 'answers',
+                ],
+            ],
+        ]);
+
+        $index->setMapping($mappingQuestion);
+        $index->addDocuments([
+            $index->createDocument(1, [
+                'last_activity_date' => '2015-01-05',
+                'title' => 'Question about linux #1',
+                'my_join_field' => [
+                    'name' => 'questions',
+                ],
+            ]),
+            $index->createDocument(2, [
+                'last_activity_date' => '2014-12-23',
+                'title' => 'Question about linux #2',
+                'my_join_field' => [
+                    'name' => 'questions',
+                ],
+            ]),
+            $index->createDocument(3, [
+                'last_activity_date' => '2015-01-05',
+                'title' => 'Question about windows #1',
+                'my_join_field' => [
+                    'name' => 'questions',
+                ],
+            ]),
+            $index->createDocument(4, [
+                'last_activity_date' => '2014-12-23',
+                'title' => 'Question about windows #2',
+                'my_join_field' => [
+                    'name' => 'questions',
+                ],
+            ]),
+            $index->createDocument(5, [
+                'last_activity_date' => '2014-12-23',
+                'title' => 'Question about osx',
+                'my_join_field' => [
+                    'name' => 'questions',
+                ],
+            ]),
+        ]);
+
+        $doc1 = $index->createDocument(6, [
+            'answer' => 'linux is cool',
+            'last_activity_date' => '2016-01-05',
+            'my_join_field' => [
+                'name' => 'answers',
+                'parent' => 1,
+            ],
+        ]);
+
+        $doc2 = $index->createDocument(7, [
+            'answer' => 'linux is bad',
+            'last_activity_date' => '2005-01-05',
+            'my_join_field' => [
+                'name' => 'answers',
+                'parent' => 1,
+            ],
+        ]);
+
+        $doc3 = $index->createDocument(8, [
+            'answer' => 'windows was cool',
+            'last_activity_date' => '2005-01-05',
+            'my_join_field' => [
+                'name' => 'answers',
+                'parent' => 2,
+            ],
+        ]);
+
+        $this->_getClient()->addDocuments([$doc1, $doc2, $doc3], ['routing' => 1]);
+
+        $index->refresh();
+
+        return $index;
+    }
+
+    private function getNestedQuery(AbstractQuery $query, InnerHits $innerHits)
+    {
+        $nested = (new Nested())
+            ->setInnerHits($innerHits)
+            ->setPath('users')
+            ->setQuery($query)
+        ;
+
+        return $this->_getIndexForNestedTest()->search($nested);
+    }
+
+    private function getParentChildQuery(AbstractQuery $query, InnerHits $innerHits)
+    {
+        $child = (new HasChild($query, 'answers'))->setInnerHits($innerHits);
+
+        return $this->_getIndexForParentChildrenTest()->search($child);
+    }
 }
diff --git a/tests/Query/LimitTest.php b/tests/Query/LimitTest.php
index cc815ceb79..6e53318132 100644
--- a/tests/Query/LimitTest.php
+++ b/tests/Query/LimitTest.php
@@ -5,12 +5,15 @@
 use Elastica\Query\Limit;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class LimitTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testSetType()
+    public function testSetType(): void
     {
         $query = new Limit(10);
         $this->assertEquals(10, $query->getParam('value'));
@@ -22,7 +25,7 @@ public function testSetType()
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $query = new Limit(15);
 
diff --git a/tests/Query/MatchAllTest.php b/tests/Query/MatchAllTest.php
index 2dc02f9ebd..df45e9cadb 100644
--- a/tests/Query/MatchAllTest.php
+++ b/tests/Query/MatchAllTest.php
@@ -7,12 +7,15 @@
 use Elastica\Search;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class MatchAllTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $query = new MatchAll();
 
@@ -24,7 +27,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testMatchAllIndicesTypes()
+    public function testMatchAllIndicesTypes(): void
     {
         $index1 = $this->_createIndex();
 
diff --git a/tests/Query/MatchNoneTest.php b/tests/Query/MatchNoneTest.php
index da6643d893..ec1d78b26b 100644
--- a/tests/Query/MatchNoneTest.php
+++ b/tests/Query/MatchNoneTest.php
@@ -7,12 +7,15 @@
 use Elastica\Search;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class MatchNoneTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $query = new MatchNone();
 
@@ -24,7 +27,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testMatchNone()
+    public function testMatchNone(): void
     {
         $index = $this->_createIndex();
         $client = $index->getClient();
diff --git a/tests/Query/MatchPhrasePrefixTest.php b/tests/Query/MatchPhrasePrefixTest.php
index 4f86cc67f0..3fec0a9de5 100644
--- a/tests/Query/MatchPhrasePrefixTest.php
+++ b/tests/Query/MatchPhrasePrefixTest.php
@@ -6,12 +6,15 @@
 use Elastica\Query\MatchPhrasePrefix;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class MatchPhrasePrefixTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $field = 'test';
         $testQuery = 'Nicolas Ruflin';
@@ -42,7 +45,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testMatchPhrasePrefix()
+    public function testMatchPhrasePrefix(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('test');
diff --git a/tests/Query/MatchPhraseTest.php b/tests/Query/MatchPhraseTest.php
index dcc1341dcc..58d7e2032c 100644
--- a/tests/Query/MatchPhraseTest.php
+++ b/tests/Query/MatchPhraseTest.php
@@ -6,12 +6,15 @@
 use Elastica\Query\MatchPhrase;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class MatchPhraseTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $field = 'test';
         $testQuery = 'Nicolas Ruflin';
@@ -39,7 +42,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testMatchPhrase()
+    public function testMatchPhrase(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('test');
diff --git a/tests/Query/MatchTest.php b/tests/Query/MatchTest.php
index 6ab9c949f1..ee1676a781 100644
--- a/tests/Query/MatchTest.php
+++ b/tests/Query/MatchTest.php
@@ -6,12 +6,15 @@
 use Elastica\Query\Match;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class MatchTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $field = 'test';
         $testQuery = 'Nicolas Ruflin';
@@ -59,7 +62,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testMatch()
+    public function testMatch(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('test');
@@ -89,7 +92,7 @@ public function testMatch()
     /**
      * @group functional
      */
-    public function testMatchSetFieldBoost()
+    public function testMatchSetFieldBoost(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('test');
@@ -120,7 +123,7 @@ public function testMatchSetFieldBoost()
     /**
      * @group functional
      */
-    public function testMatchSetFieldBoostWithString()
+    public function testMatchSetFieldBoostWithString(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('test');
@@ -151,7 +154,7 @@ public function testMatchSetFieldBoostWithString()
     /**
      * @group functional
      */
-    public function testMatchZeroTerm()
+    public function testMatchZeroTerm(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('test');
@@ -176,7 +179,7 @@ public function testMatchZeroTerm()
     /**
      * @group unit
      */
-    public function testMatchFuzzinessType()
+    public function testMatchFuzzinessType(): void
     {
         $field = 'test';
         $query = new Match();
@@ -197,7 +200,7 @@ public function testMatchFuzzinessType()
     /**
      * @group unit
      */
-    public function testConstruct()
+    public function testConstruct(): void
     {
         $match = new Match(null, 'values');
         $this->assertEquals(['match' => []], $match->toArray());
diff --git a/tests/Query/MoreLikeThisTest.php b/tests/Query/MoreLikeThisTest.php
index 9e48ffab1e..d8b5f40163 100644
--- a/tests/Query/MoreLikeThisTest.php
+++ b/tests/Query/MoreLikeThisTest.php
@@ -11,12 +11,15 @@
 use Elastica\Query\Term;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class MoreLikeThisTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testSearch()
+    public function testSearch(): void
     {
         $client = $this->_getClient();
         $index = new Index($client, 'test');
@@ -58,7 +61,7 @@ public function testSearch()
     /**
      * @group functional
      */
-    public function testSearchByDocument()
+    public function testSearchByDocument(): void
     {
         $client = $this->_getClient(['persistent' => false]);
         $index = $client->getIndex('elastica_test');
@@ -115,7 +118,7 @@ public function testSearchByDocument()
     /**
      * @group unit
      */
-    public function testSetFields()
+    public function testSetFields(): void
     {
         $query = new MoreLikeThis();
 
@@ -129,7 +132,7 @@ public function testSetFields()
     /**
      * @group unit
      */
-    public function testSetLike()
+    public function testSetLike(): void
     {
         $query = new MoreLikeThis();
         $query->setLike(' hello world');
@@ -141,7 +144,7 @@ public function testSetLike()
     /**
      * @group unit
      */
-    public function testSetBoost()
+    public function testSetBoost(): void
     {
         $query = new MoreLikeThis();
 
@@ -154,7 +157,7 @@ public function testSetBoost()
     /**
      * @group unit
      */
-    public function testSetMaxQueryTerms()
+    public function testSetMaxQueryTerms(): void
     {
         $query = new MoreLikeThis();
 
@@ -167,7 +170,7 @@ public function testSetMaxQueryTerms()
     /**
      * @group unit
      */
-    public function testSetMinimumShouldMatch()
+    public function testSetMinimumShouldMatch(): void
     {
         $query = new MoreLikeThis();
 
@@ -180,7 +183,7 @@ public function testSetMinimumShouldMatch()
     /**
      * @group unit
      */
-    public function testSetMinDocFrequency()
+    public function testSetMinDocFrequency(): void
     {
         $query = new MoreLikeThis();
 
@@ -193,7 +196,7 @@ public function testSetMinDocFrequency()
     /**
      * @group unit
      */
-    public function testSetMaxDocFrequency()
+    public function testSetMaxDocFrequency(): void
     {
         $query = new MoreLikeThis();
 
@@ -206,7 +209,7 @@ public function testSetMaxDocFrequency()
     /**
      * @group unit
      */
-    public function testSetMinWordLength()
+    public function testSetMinWordLength(): void
     {
         $query = new MoreLikeThis();
 
@@ -219,7 +222,7 @@ public function testSetMinWordLength()
     /**
      * @group unit
      */
-    public function testSetMaxWordLength()
+    public function testSetMaxWordLength(): void
     {
         $query = new MoreLikeThis();
 
@@ -232,7 +235,7 @@ public function testSetMaxWordLength()
     /**
      * @group unit
      */
-    public function testSetBoostTerms()
+    public function testSetBoostTerms(): void
     {
         $query = new MoreLikeThis();
 
@@ -245,7 +248,7 @@ public function testSetBoostTerms()
     /**
      * @group unit
      */
-    public function testSetAnalyzer()
+    public function testSetAnalyzer(): void
     {
         $query = new MoreLikeThis();
 
@@ -258,7 +261,7 @@ public function testSetAnalyzer()
     /**
      * @group unit
      */
-    public function testSetStopWords()
+    public function testSetStopWords(): void
     {
         $query = new MoreLikeThis();
 
@@ -271,7 +274,7 @@ public function testSetStopWords()
     /**
      * @group unit
      */
-    public function testToArrayForId()
+    public function testToArrayForId(): void
     {
         $query = new MoreLikeThis();
         $query->setLike(new Document('1', [], 'index'));
@@ -293,7 +296,7 @@ public function testToArrayForId()
     /**
      * @group unit
      */
-    public function testToArrayForSource()
+    public function testToArrayForSource(): void
     {
         $query = new MoreLikeThis();
         $query->setLike(new Document('', ['Foo' => 'Bar'], 'index'));
diff --git a/tests/Query/MultiMatchTest.php b/tests/Query/MultiMatchTest.php
index b8eec5311c..4b6eb28628 100644
--- a/tests/Query/MultiMatchTest.php
+++ b/tests/Query/MultiMatchTest.php
@@ -9,6 +9,9 @@
 use Elastica\Query\MultiMatch;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class MultiMatchTest extends BaseTest
 {
     private $index;
@@ -24,7 +27,7 @@ class MultiMatchTest extends BaseTest
     /**
      * @group functional
      */
-    public function testMinimumShouldMatch()
+    public function testMinimumShouldMatch(): void
     {
         $multiMatch = new MultiMatch();
         $multiMatch->setQuery('Tristan Maindron');
@@ -38,7 +41,7 @@ public function testMinimumShouldMatch()
     /**
      * @group functional
      */
-    public function testAndOperator()
+    public function testAndOperator(): void
     {
         $multiMatch = new MultiMatch();
         $multiMatch->setQuery('Monique Maindron');
@@ -52,7 +55,7 @@ public function testAndOperator()
     /**
      * @group functional
      */
-    public function testType()
+    public function testType(): void
     {
         $multiMatch = new MultiMatch();
         $multiMatch->setQuery('Trist');
@@ -66,7 +69,7 @@ public function testType()
     /**
      * @group functional
      */
-    public function testFuzzy()
+    public function testFuzzy(): void
     {
         $multiMatch = new MultiMatch();
         $multiMatch->setQuery('Tritsan'); // Misspell on purpose
@@ -96,7 +99,7 @@ public function testFuzzy()
     /**
      * @group functional
      */
-    public function testFuzzyWithOptions1()
+    public function testFuzzyWithOptions1(): void
     {
         // Here Elasticsearch will not accept mispells
         // on the first 6 letters.
@@ -113,7 +116,7 @@ public function testFuzzyWithOptions1()
     /**
      * @group functional
      */
-    public function testFuzzyWithOptions2()
+    public function testFuzzyWithOptions2(): void
     {
         // Here with a 'M' search we should hit 'Moraes' first
         // and then stop because MaxExpansion = 1.
@@ -132,7 +135,7 @@ public function testFuzzyWithOptions2()
     /**
      * @group functional
      */
-    public function testZeroTerm()
+    public function testZeroTerm(): void
     {
         $multiMatch = new MultiMatch();
         $multiMatch->setQuery('not'); // This is a stopword.
@@ -152,7 +155,7 @@ public function testZeroTerm()
     /**
      * @group functional
      */
-    public function testBaseMultiMatch()
+    public function testBaseMultiMatch(): void
     {
         $multiMatch = new MultiMatch();
         $multiMatch->setQuery('Rodolfo');
diff --git a/tests/Query/NestedTest.php b/tests/Query/NestedTest.php
index 1be8b019e5..e26b77c2e9 100644
--- a/tests/Query/NestedTest.php
+++ b/tests/Query/NestedTest.php
@@ -6,12 +6,15 @@
 use Elastica\Query\QueryString;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class NestedTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testSetQuery()
+    public function testSetQuery(): void
     {
         $nested = new Nested();
         $path = 'test1';
diff --git a/tests/Query/ParentIdTest.php b/tests/Query/ParentIdTest.php
index a7cea4fbe3..0ca657cdce 100644
--- a/tests/Query/ParentIdTest.php
+++ b/tests/Query/ParentIdTest.php
@@ -7,12 +7,15 @@
 use Elastica\Search;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class ParentIdTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $query = new ParentId('join', '1');
         $expectedArray = [
@@ -29,7 +32,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testParentId()
+    public function testParentId(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('testparentid');
@@ -120,7 +123,7 @@ public function testParentId()
     /**
      * @group unit
      */
-    public function testQueryBuilderParentId()
+    public function testQueryBuilderParentId(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('testparentid');
diff --git a/tests/Query/PercolateTest.php b/tests/Query/PercolateTest.php
index 057b773df2..fb621d77cd 100644
--- a/tests/Query/PercolateTest.php
+++ b/tests/Query/PercolateTest.php
@@ -7,6 +7,9 @@
 use Elastica\Query\Percolate;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class PercolateTest extends BaseTest
 {
     /**
@@ -17,7 +20,7 @@ class PercolateTest extends BaseTest
     /**
      * @group functional
      */
-    public function testPercolateQueryOnNewDocument()
+    public function testPercolateQueryOnNewDocument(): void
     {
         $this->_prepareIndexForPercolate();
         //Register a query in the percolator:
@@ -28,7 +31,8 @@ public function testPercolateQueryOnNewDocument()
         //Match a document to the registered percolator queries:
         $percolateQuery = new Percolate();
         $percolateQuery->setField('query')
-            ->setDocument($doc->getData());
+            ->setDocument($doc->getData())
+        ;
         $resultSet = $this->index->search($percolateQuery);
 
         $this->assertEquals(1, $resultSet->count());
@@ -46,7 +50,8 @@ public function testPercolateQueryOnNewDocument()
         $doc2 = new Document(4, ['message' => 'Just a simple text for test']);
         $percolateQuery = new Percolate();
         $percolateQuery->setField('query')
-            ->setDocument($doc2->getData());
+            ->setDocument($doc2->getData())
+        ;
         $resultSet = $this->index->search($percolateQuery);
 
         $this->assertEquals(0, $resultSet->count());
@@ -55,7 +60,7 @@ public function testPercolateQueryOnNewDocument()
     /**
      * @group functional
      */
-    public function testPercolateQueryOnExistingDocument()
+    public function testPercolateQueryOnExistingDocument(): void
     {
         $this->_prepareIndexForPercolate();
         //Register a query in the percolator:
@@ -68,7 +73,8 @@ public function testPercolateQueryOnExistingDocument()
         $percolateQuery = new Percolate();
         $percolateQuery->setField('query')
             ->setDocumentIndex($this->index->getName())
-            ->setDocumentId($doc->getId());
+            ->setDocumentId($doc->getId())
+        ;
         $resultSet = $this->index->search($percolateQuery);
 
         $this->assertEquals(1, $resultSet->count());
@@ -85,26 +91,17 @@ public function testPercolateQueryOnExistingDocument()
         $percolateQuery = new Percolate();
         $percolateQuery->setField('query')
             ->setDocumentIndex($this->index->getName())
-            ->setDocumentId($doc2->getId());
+            ->setDocumentId($doc2->getId())
+        ;
         $resultSet = $this->index->search($percolateQuery);
 
         $this->assertEquals(0, $resultSet->count());
     }
 
-    private function _prepareIndexForPercolate()
-    {
-        $this->index = $this->_createIndex();
-        $this->index->getSettings()->setNumberOfReplicas(0);
-        //The doctype mapping is the mapping used to preprocess the document
-        // defined in the percolator query before it gets indexed into a temporary index.
-        //The queries mapping is the mapping used for indexing the query documents.
-        $this->index->setMapping(new Mapping(['message' => ['type' => 'text'], 'query' => ['type' => 'percolator']]));
-    }
-
     /**
      * @group unit
      */
-    public function testSetField()
+    public function testSetField(): void
     {
         $field = 'field1';
         $query = new Percolate();
@@ -118,7 +115,7 @@ public function testSetField()
     /**
      * @group unit
      */
-    public function testSetDocument()
+    public function testSetDocument(): void
     {
         $query = new Percolate();
         $doc = new Document(1, ['message' => 'A new bonsai tree in the office']);
@@ -132,7 +129,7 @@ public function testSetDocument()
     /**
      * @group unit
      */
-    public function testSetDocumentIndex()
+    public function testSetDocumentIndex(): void
     {
         $index = $this->_createIndex('indexone');
         $query = new Percolate();
@@ -146,7 +143,7 @@ public function testSetDocumentIndex()
     /**
      * @group unit
      */
-    public function testSetDocumentId()
+    public function testSetDocumentId(): void
     {
         $id = 3;
         $query = new Percolate();
@@ -160,7 +157,7 @@ public function testSetDocumentId()
     /**
      * @group unit
      */
-    public function testSetDocumentRouting()
+    public function testSetDocumentRouting(): void
     {
         $routing = 'testRout';
         $query = new Percolate();
@@ -174,7 +171,7 @@ public function testSetDocumentRouting()
     /**
      * @group unit
      */
-    public function testSetDocumentPreference()
+    public function testSetDocumentPreference(): void
     {
         $preference = ['pref1' => 'test', 'pref2' => 'test2'];
         $query = new Percolate();
@@ -188,7 +185,7 @@ public function testSetDocumentPreference()
     /**
      * @group unit
      */
-    public function testSetDocumentVersion()
+    public function testSetDocumentVersion(): void
     {
         $version = 10;
         $query = new Percolate();
@@ -198,4 +195,14 @@ public function testSetDocumentVersion()
 
         $this->assertEquals($data['percolate']['version'], $version);
     }
+
+    private function _prepareIndexForPercolate(): void
+    {
+        $this->index = $this->_createIndex();
+        $this->index->getSettings()->setNumberOfReplicas(0);
+        //The doctype mapping is the mapping used to preprocess the document
+        // defined in the percolator query before it gets indexed into a temporary index.
+        //The queries mapping is the mapping used for indexing the query documents.
+        $this->index->setMapping(new Mapping(['message' => ['type' => 'text'], 'query' => ['type' => 'percolator']]));
+    }
 }
diff --git a/tests/Query/PostFilterTest.php b/tests/Query/PostFilterTest.php
index 2ebe19d01b..d800cf0b20 100644
--- a/tests/Query/PostFilterTest.php
+++ b/tests/Query/PostFilterTest.php
@@ -8,27 +8,15 @@
 use Elastica\Query\Term;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class PostFilterTest extends BaseTest
 {
-    protected function _getTestIndex()
-    {
-        $index = $this->_createIndex();
-        $docs = [
-            new Document(1, ['color' => 'green', 'make' => 'ford']),
-            new Document(2, ['color' => 'blue', 'make' => 'volvo']),
-            new Document(3, ['color' => 'red', 'make' => 'ford']),
-            new Document(4, ['color' => 'green', 'make' => 'renault']),
-        ];
-        $index->addDocuments($docs);
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $query = new Query();
 
@@ -44,7 +32,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testQuery()
+    public function testQuery(): void
     {
         $query = new Query();
 
@@ -60,4 +48,19 @@ public function testQuery()
 
         $this->assertEquals(1, $this->_getTestIndex()->count($query));
     }
+
+    protected function _getTestIndex()
+    {
+        $index = $this->_createIndex();
+        $docs = [
+            new Document(1, ['color' => 'green', 'make' => 'ford']),
+            new Document(2, ['color' => 'blue', 'make' => 'volvo']),
+            new Document(3, ['color' => 'red', 'make' => 'ford']),
+            new Document(4, ['color' => 'green', 'make' => 'renault']),
+        ];
+        $index->addDocuments($docs);
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Query/PrefixTest.php b/tests/Query/PrefixTest.php
index 070097fe6b..cdce2d1fd3 100644
--- a/tests/Query/PrefixTest.php
+++ b/tests/Query/PrefixTest.php
@@ -5,12 +5,15 @@
 use Elastica\Query\Prefix;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class PrefixTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $query = new Prefix();
         $key = 'name';
diff --git a/tests/Query/QueryStringTest.php b/tests/Query/QueryStringTest.php
index 9a39dc7474..b2433d0822 100644
--- a/tests/Query/QueryStringTest.php
+++ b/tests/Query/QueryStringTest.php
@@ -7,12 +7,15 @@
 use Elastica\Query\QueryString;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class QueryStringTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testSearchMultipleFields()
+    public function testSearchMultipleFields(): void
     {
         $str = \md5(\rand());
         $query = new QueryString($str);
@@ -44,7 +47,7 @@ public function testSearchMultipleFields()
     /**
      * @group functional
      */
-    public function testSearch()
+    public function testSearch(): void
     {
         $index = $this->_createIndex();
         $index->getSettings()->setNumberOfReplicas(0);
@@ -64,7 +67,7 @@ public function testSearch()
      *
      * @group functional
      */
-    public function testSearchFields()
+    public function testSearchFields(): void
     {
         $index = $this->_createIndex();
 
@@ -85,7 +88,7 @@ public function testSearchFields()
      *
      * @group functional
      */
-    public function testSearchFieldsValidationException()
+    public function testSearchFieldsValidationException(): void
     {
         $index = $this->_createIndex();
 
@@ -116,7 +119,7 @@ public function testSearchFieldsValidationException()
     /**
      * @group unit
      */
-    public function testSetDefaultOperator()
+    public function testSetDefaultOperator(): void
     {
         $operator = 'AND';
         $query = new QueryString('test');
@@ -130,7 +133,7 @@ public function testSetDefaultOperator()
     /**
      * @group unit
      */
-    public function testSetDefaultField()
+    public function testSetDefaultField(): void
     {
         $default = 'field1';
         $query = new QueryString('test');
@@ -144,7 +147,7 @@ public function testSetDefaultField()
     /**
      * @group unit
      */
-    public function testSetAnalyzer()
+    public function testSetAnalyzer(): void
     {
         $value = 'test';
         $query = new QueryString('test');
@@ -156,7 +159,7 @@ public function testSetAnalyzer()
     /**
      * @group unit
      */
-    public function testSetAllowLeadingWildcard()
+    public function testSetAllowLeadingWildcard(): void
     {
         $value = true;
         $query = new QueryString('test');
@@ -168,7 +171,7 @@ public function testSetAllowLeadingWildcard()
     /**
      * @group unit
      */
-    public function testSetEnablePositionIncrements()
+    public function testSetEnablePositionIncrements(): void
     {
         $value = true;
         $query = new QueryString('test');
@@ -180,7 +183,7 @@ public function testSetEnablePositionIncrements()
     /**
      * @group unit
      */
-    public function testSetFuzzyPrefixLength()
+    public function testSetFuzzyPrefixLength(): void
     {
         $value = 1;
         $query = new QueryString('test');
@@ -192,7 +195,7 @@ public function testSetFuzzyPrefixLength()
     /**
      * @group unit
      */
-    public function testSetFuzzyMinSim()
+    public function testSetFuzzyMinSim(): void
     {
         $value = 0.1;
         $query = new QueryString('test');
@@ -204,7 +207,7 @@ public function testSetFuzzyMinSim()
     /**
      * @group unit
      */
-    public function testSetAnalyzeWildcard()
+    public function testSetAnalyzeWildcard(): void
     {
         $value = true;
         $query = new QueryString('test');
@@ -216,7 +219,7 @@ public function testSetAnalyzeWildcard()
     /**
      * @group unit
      */
-    public function testSetTieBreaker()
+    public function testSetTieBreaker(): void
     {
         $value = 0.2;
         $query = new QueryString('test');
@@ -228,7 +231,7 @@ public function testSetTieBreaker()
     /**
      * @group unit
      */
-    public function testSetRewrite()
+    public function testSetRewrite(): void
     {
         $rewrite = 'scoring_boolean';
         $query = new QueryString('test');
@@ -242,7 +245,7 @@ public function testSetRewrite()
     /**
      * @group unit
      */
-    public function testSetTimezone()
+    public function testSetTimezone(): void
     {
         $timezone = 'Europe/Paris';
         $text = 'date:[2012 TO 2014]';
@@ -264,7 +267,7 @@ public function testSetTimezone()
     /**
      * @group unit
      */
-    public function testSetPhraseSlop()
+    public function testSetPhraseSlop(): void
     {
         $phraseSlop = 9;
 
@@ -278,7 +281,7 @@ public function testSetPhraseSlop()
     /**
      * @group functional
      */
-    public function testSetBoost()
+    public function testSetBoost(): void
     {
         $index = $this->_createIndex();
         $query = new QueryString('test');
diff --git a/tests/Query/RangeTest.php b/tests/Query/RangeTest.php
index f26a5dcb30..81f9d1b97d 100644
--- a/tests/Query/RangeTest.php
+++ b/tests/Query/RangeTest.php
@@ -6,12 +6,15 @@
 use Elastica\Query\Range;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class RangeTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testQuery()
+    public function testQuery(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('test');
@@ -41,7 +44,7 @@ public function testQuery()
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $range = new Range();
 
@@ -60,7 +63,7 @@ public function testToArray()
     /**
      * @group unit
      */
-    public function testConstruct()
+    public function testConstruct(): void
     {
         $ranges = ['from' => 20, 'to' => 40];
         $range = new Range(
diff --git a/tests/Query/RegexpTest.php b/tests/Query/RegexpTest.php
index eb2f07820e..11e8e2fe7c 100644
--- a/tests/Query/RegexpTest.php
+++ b/tests/Query/RegexpTest.php
@@ -5,12 +5,15 @@
 use Elastica\Query\Regexp;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class RegexpTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $field = 'name';
         $value = 'ruf';
diff --git a/tests/Query/RescoreTest.php b/tests/Query/RescoreTest.php
index e26c3a9c31..f2cfdb5b7e 100644
--- a/tests/Query/RescoreTest.php
+++ b/tests/Query/RescoreTest.php
@@ -8,12 +8,15 @@
 use Elastica\Rescore\Query as QueryRescore;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class RescoreTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $query = new Query();
         $mainQuery = new Match();
@@ -53,7 +56,7 @@ public function testToArray()
     /**
      * @group unit
      */
-    public function testSetSize()
+    public function testSetSize(): void
     {
         $query = new Query();
         $mainQuery = new Match();
@@ -95,7 +98,7 @@ public function testSetSize()
     /**
      * @group unit
      */
-    public function testSetWeights()
+    public function testSetWeights(): void
     {
         $query = new Query();
         $mainQuery = new Match();
@@ -141,7 +144,7 @@ public function testSetWeights()
     /**
      * @group functional
      */
-    public function testMultipleQueries()
+    public function testMultipleQueries(): void
     {
         $query = new Query();
         $mainQuery = new Match();
@@ -213,7 +216,7 @@ public function testMultipleQueries()
     /**
      * @group functional
      */
-    public function testQuery()
+    public function testQuery(): void
     {
         $query = new Query();
         $mainQuery = new Match();
diff --git a/tests/Query/ScriptTest.php b/tests/Query/ScriptTest.php
index 8351486645..f2e70d9bbf 100644
--- a/tests/Query/ScriptTest.php
+++ b/tests/Query/ScriptTest.php
@@ -6,12 +6,15 @@
 use Elastica\Script\Script;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class ScriptTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $string = '_score * 2.0';
 
@@ -33,7 +36,7 @@ public function testToArray()
     /**
      * @group unit
      */
-    public function testSetScript()
+    public function testSetScript(): void
     {
         $string = '_score * 2.0';
         $params = [
diff --git a/tests/Query/SimpleQueryStringTest.php b/tests/Query/SimpleQueryStringTest.php
index 174384af3c..73e8c4b2fd 100644
--- a/tests/Query/SimpleQueryStringTest.php
+++ b/tests/Query/SimpleQueryStringTest.php
@@ -6,12 +6,15 @@
 use Elastica\Query\SimpleQueryString;
 use Elastica\Test\Base;
 
+/**
+ * @internal
+ */
 class SimpleQueryStringTest extends Base
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $string = 'this is a test';
         $fields = ['field1', 'field2'];
@@ -34,7 +37,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testQuery()
+    public function testQuery(): void
     {
         $index = $this->_createIndex();
         $docs = [
@@ -62,7 +65,7 @@ public function testQuery()
     /**
      * @group unit
      */
-    public function testSetMinimumShouldMatch()
+    public function testSetMinimumShouldMatch(): void
     {
         $expected = [
             'simple_query_string' => [
@@ -81,7 +84,7 @@ public function testSetMinimumShouldMatch()
     /**
      * @group functional
      */
-    public function testSetMinimumShouldMatchWorks()
+    public function testSetMinimumShouldMatchWorks(): void
     {
         $this->_checkVersion('1.5');
 
diff --git a/tests/Query/SimpleTest.php b/tests/Query/SimpleTest.php
index 65dcbe5957..a48a65453a 100644
--- a/tests/Query/SimpleTest.php
+++ b/tests/Query/SimpleTest.php
@@ -5,12 +5,15 @@
 use Elastica\Query\Simple;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class SimpleTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $testQuery = ['hello' => ['world'], 'name' => 'ruflin'];
         $query = new Simple($testQuery);
diff --git a/tests/Query/SpanContainingTest.php b/tests/Query/SpanContainingTest.php
index f4f2701791..6db60a310a 100644
--- a/tests/Query/SpanContainingTest.php
+++ b/tests/Query/SpanContainingTest.php
@@ -8,12 +8,15 @@
 use Elastica\Query\SpanTerm;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class SpanContainingTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $field = 'name';
         $spanTermQuery1 = new SpanTerm([$field => 'nicolas']);
@@ -60,7 +63,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testSpanContaining()
+    public function testSpanContaining(): void
     {
         $field = 'lorem';
         $value = 'Lorem ipsum dolor sit amet, consectetur adipiscing elit. Suspendisse odio lacus, aliquam nec nulla quis, aliquam eleifend eros.';
diff --git a/tests/Query/SpanFirstTest.php b/tests/Query/SpanFirstTest.php
index 21a4930f62..4144cdb165 100644
--- a/tests/Query/SpanFirstTest.php
+++ b/tests/Query/SpanFirstTest.php
@@ -7,12 +7,15 @@
 use Elastica\Query\SpanTerm;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class SpanFirstTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $query = new SpanFirst();
         $query->setMatch(new SpanTerm(['user' => 'kimchy']));
@@ -33,7 +36,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testSpanNearTerm()
+    public function testSpanNearTerm(): void
     {
         $field = 'lorem';
         $value = 'Lorem ipsum dolor sit amet, consectetur adipiscing elit. Suspendisse odio lacus, aliquam nec nulla quis, aliquam eleifend eros.';
diff --git a/tests/Query/SpanMultiTest.php b/tests/Query/SpanMultiTest.php
index da6eb98887..056691f81e 100644
--- a/tests/Query/SpanMultiTest.php
+++ b/tests/Query/SpanMultiTest.php
@@ -10,12 +10,15 @@
 use Elastica\Query\Wildcard;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class SpanMultiTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testConstructValid()
+    public function testConstructValid(): void
     {
         $field = 'name';
         $value = 'marek';
@@ -56,7 +59,7 @@ public function testConstructValid()
     /**
      * @group functional
      */
-    public function testSpanMulti()
+    public function testSpanMulti(): void
     {
         $field = 'lorem';
         $text1 = 'Lorem ipsum dolor sit amet, consectetur adipiscing elit.';
diff --git a/tests/Query/SpanNearTest.php b/tests/Query/SpanNearTest.php
index 0fabba34b4..e5b50e4530 100644
--- a/tests/Query/SpanNearTest.php
+++ b/tests/Query/SpanNearTest.php
@@ -8,12 +8,15 @@
 use Elastica\Query\Term;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class SpanNearTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testConstructWrongTypeInvalid()
+    public function testConstructWrongTypeInvalid(): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
 
@@ -25,7 +28,7 @@ public function testConstructWrongTypeInvalid()
     /**
      * @group unit
      */
-    public function testConstructValid()
+    public function testConstructValid(): void
     {
         $field = 'name';
         $spanTermQuery1 = new SpanTerm([$field => ['value' => 'marek', 'boost' => 1.5]]);
@@ -61,7 +64,7 @@ public function testConstructValid()
     /**
      * @group functional
      */
-    public function testSpanNearTerm()
+    public function testSpanNearTerm(): void
     {
         $field = 'lorem';
         $value = 'Lorem ipsum dolor sit amet, consectetur adipiscing elit. Suspendisse odio lacus, aliquam nec nulla quis, aliquam eleifend eros.';
diff --git a/tests/Query/SpanNotTest.php b/tests/Query/SpanNotTest.php
index 1c764595c5..66290f8c5c 100644
--- a/tests/Query/SpanNotTest.php
+++ b/tests/Query/SpanNotTest.php
@@ -8,12 +8,15 @@
 use Elastica\Query\SpanTerm;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class SpanNotTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $field = 'name';
         $spanTermQuery1 = new SpanTerm([$field => 'nicolas']);
@@ -60,7 +63,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testSpanNot()
+    public function testSpanNot(): void
     {
         $field = 'lorem';
         $value = 'Lorem ipsum dolor sit amet, consectetur adipiscing elit. Suspendisse odio lacus, aliquam nec nulla quis, aliquam eleifend eros.';
diff --git a/tests/Query/SpanOrTest.php b/tests/Query/SpanOrTest.php
index e013a81514..892dc9c290 100644
--- a/tests/Query/SpanOrTest.php
+++ b/tests/Query/SpanOrTest.php
@@ -8,12 +8,15 @@
 use Elastica\Query\Term;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class SpanOrTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testConstructWrongTypeInvalid()
+    public function testConstructWrongTypeInvalid(): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
 
@@ -25,7 +28,7 @@ public function testConstructWrongTypeInvalid()
     /**
      * @group unit
      */
-    public function testConstructValid()
+    public function testConstructValid(): void
     {
         $field = 'name';
         $spanTermQuery1 = new SpanTerm([$field => ['value' => 'marek', 'boost' => 1.5]]);
@@ -59,7 +62,7 @@ public function testConstructValid()
     /**
      * @group functional
      */
-    public function testSpanOrTerm()
+    public function testSpanOrTerm(): void
     {
         $field = 'lorem';
         $text1 = 'Lorem ipsum dolor sit amet, consectetur adipiscing elit.';
diff --git a/tests/Query/SpanTermTest.php b/tests/Query/SpanTermTest.php
index a5f1665598..d3e4356e49 100644
--- a/tests/Query/SpanTermTest.php
+++ b/tests/Query/SpanTermTest.php
@@ -6,12 +6,15 @@
 use Elastica\Query\SpanTerm;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class SpanTermTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testConstruct()
+    public function testConstruct(): void
     {
         $field = 'name';
         $value = 'marek';
@@ -29,7 +32,7 @@ public function testConstruct()
     /**
      * @group functional
      */
-    public function testSpanTerm()
+    public function testSpanTerm(): void
     {
         $field = 'name';
         $value = 'match';
diff --git a/tests/Query/SpanWithinTest.php b/tests/Query/SpanWithinTest.php
index 3623d10443..051eb5feae 100644
--- a/tests/Query/SpanWithinTest.php
+++ b/tests/Query/SpanWithinTest.php
@@ -8,12 +8,15 @@
 use Elastica\Query\SpanWithin;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class SpanWithinTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $field = 'name';
         $spanTermQuery1 = new SpanTerm([$field => 'nicolas']);
@@ -60,7 +63,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testSpanWithin()
+    public function testSpanWithin(): void
     {
         $field = 'lorem';
         $value = 'Lorem ipsum dolor sit amet, consectetur adipiscing elit. Suspendisse odio lacus, aliquam nec nulla quis, aliquam eleifend eros.';
diff --git a/tests/Query/TermTest.php b/tests/Query/TermTest.php
index 40a42bfc81..d5b7ef70f3 100644
--- a/tests/Query/TermTest.php
+++ b/tests/Query/TermTest.php
@@ -5,12 +5,15 @@
 use Elastica\Query\Term;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class TermTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $query = new Term();
         $key = 'name';
@@ -29,7 +32,7 @@ public function testToArray()
     /**
      * @group unit
      */
-    public function testDiacriticsValueToArray()
+    public function testDiacriticsValueToArray(): void
     {
         $query = new Term();
         $key = 'name';
diff --git a/tests/Query/TermsTest.php b/tests/Query/TermsTest.php
index 7fd9e97023..99e7063026 100644
--- a/tests/Query/TermsTest.php
+++ b/tests/Query/TermsTest.php
@@ -7,12 +7,15 @@
 use Elastica\Query\Terms;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class TermsTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testFilteredSearch()
+    public function testFilteredSearch(): void
     {
         $index = $this->_createIndex();
 
@@ -40,7 +43,7 @@ public function testFilteredSearch()
     /**
      * @group functional
      */
-    public function testFilteredSearchWithLookup()
+    public function testFilteredSearchWithLookup(): void
     {
         $index = $this->_createIndex();
 
@@ -97,8 +100,10 @@ public function provideMinimumArguments()
     /**
      * @group unit
      * @dataProvider provideMinimumArguments
+     *
+     * @param mixed $minimum
      */
-    public function testSetMinimum($minimum)
+    public function testSetMinimum($minimum): void
     {
         $key = 'name';
         $terms = ['nicolas', 'ruflin'];
@@ -113,13 +118,13 @@ public function testSetMinimum($minimum)
     /**
      * @group unit
      */
-    public function testSetTermsLookup()
+    public function testSetTermsLookup(): void
     {
         $key = 'name';
         $terms = [
             'index' => 'index_name',
             'type' => 'type_name',
-             'id' => '1',
+            'id' => '1',
             'path' => 'terms',
         ];
 
@@ -132,7 +137,7 @@ public function testSetTermsLookup()
     /**
      * @group unit
      */
-    public function testInvalidParams()
+    public function testInvalidParams(): void
     {
         $this->expectException(InvalidException::class);
 
diff --git a/tests/Query/WildcardTest.php b/tests/Query/WildcardTest.php
index b7a98f3005..c87e2ac363 100644
--- a/tests/Query/WildcardTest.php
+++ b/tests/Query/WildcardTest.php
@@ -7,12 +7,15 @@
 use Elastica\Query\Wildcard;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class WildcardTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testConstructEmpty()
+    public function testConstructEmpty(): void
     {
         $wildcard = new Wildcard();
         $this->assertEmpty($wildcard->getParams());
@@ -21,7 +24,7 @@ public function testConstructEmpty()
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $key = 'name';
         $value = 'Ru*lin';
@@ -44,7 +47,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testSearchWithAnalyzer()
+    public function testSearchWithAnalyzer(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('test');
diff --git a/tests/QueryBuilder/DSL/AbstractDSLTest.php b/tests/QueryBuilder/DSL/AbstractDSLTest.php
index f84d208ec8..6034be90d7 100644
--- a/tests/QueryBuilder/DSL/AbstractDSLTest.php
+++ b/tests/QueryBuilder/DSL/AbstractDSLTest.php
@@ -8,7 +8,7 @@
 
 abstract class AbstractDSLTest extends BaseTest
 {
-    protected function _assertImplemented(DSL $dsl, string $methodName, string $className, array $arguments)
+    protected function _assertImplemented(DSL $dsl, string $methodName, string $className, array $arguments): void
     {
         // Check method existence
         $this->assertTrue(\method_exists($dsl, $methodName));
@@ -28,7 +28,7 @@ protected function _assertImplemented(DSL $dsl, string $methodName, string $clas
         }
     }
 
-    protected function _assertNotImplemented(DSL $dsl, string $methodName, array $arguments)
+    protected function _assertNotImplemented(DSL $dsl, string $methodName, array $arguments): void
     {
         try {
             \call_user_func([$dsl, $methodName], $arguments);
@@ -42,7 +42,7 @@ protected function _assertNotImplemented(DSL $dsl, string $methodName, array $ar
      * @param \ReflectionParameter[] $left
      * @param \ReflectionParameter[] $right
      */
-    protected function _assertParametersEquals(array $left, array $right)
+    protected function _assertParametersEquals(array $left, array $right): void
     {
         $countLeft = \count($left);
         $this->assertCount($countLeft, $right, 'Parameters count mismatch');
diff --git a/tests/QueryBuilder/DSL/AggregationTest.php b/tests/QueryBuilder/DSL/AggregationTest.php
index 27d0811ee4..bd964ba002 100644
--- a/tests/QueryBuilder/DSL/AggregationTest.php
+++ b/tests/QueryBuilder/DSL/AggregationTest.php
@@ -6,12 +6,15 @@
 use Elastica\Query\Exists;
 use Elastica\QueryBuilder\DSL;
 
+/**
+ * @internal
+ */
 class AggregationTest extends AbstractDSLTest
 {
     /**
      * @group unit
      */
-    public function testType()
+    public function testType(): void
     {
         $aggregationDSL = new DSL\Aggregation();
 
@@ -22,7 +25,7 @@ public function testType()
     /**
      * @group unit
      */
-    public function testInterface()
+    public function testInterface(): void
     {
         $aggregationDSL = new DSL\Aggregation();
 
diff --git a/tests/QueryBuilder/DSL/CollapseTest.php b/tests/QueryBuilder/DSL/CollapseTest.php
index 3f3bed60da..a4985bc03f 100644
--- a/tests/QueryBuilder/DSL/CollapseTest.php
+++ b/tests/QueryBuilder/DSL/CollapseTest.php
@@ -5,12 +5,15 @@
 use Elastica\Collapse;
 use Elastica\QueryBuilder\DSL;
 
+/**
+ * @internal
+ */
 class CollapseTest extends AbstractDSLTest
 {
     /**
      * @group unit
      */
-    public function testType()
+    public function testType(): void
     {
         $collapseDSL = new DSL\Collapse();
 
@@ -21,7 +24,7 @@ public function testType()
     /**
      * @group unit
      */
-    public function testInterface()
+    public function testInterface(): void
     {
         $collapseDSL = new DSL\Collapse();
 
diff --git a/tests/QueryBuilder/DSL/QueryTest.php b/tests/QueryBuilder/DSL/QueryTest.php
index 014a7dcbf9..7c0b0fb13c 100644
--- a/tests/QueryBuilder/DSL/QueryTest.php
+++ b/tests/QueryBuilder/DSL/QueryTest.php
@@ -6,12 +6,15 @@
 use Elastica\Query\Match;
 use Elastica\QueryBuilder\DSL;
 
+/**
+ * @internal
+ */
 class QueryTest extends AbstractDSLTest
 {
     /**
      * @group unit
      */
-    public function testType()
+    public function testType(): void
     {
         $queryDSL = new DSL\Query();
 
@@ -22,7 +25,7 @@ public function testType()
     /**
      * @group unit
      */
-    public function testMatch()
+    public function testMatch(): void
     {
         $queryDSL = new DSL\Query();
 
@@ -34,7 +37,7 @@ public function testMatch()
     /**
      * @group unit
      */
-    public function testInterface()
+    public function testInterface(): void
     {
         $queryDSL = new DSL\Query();
 
diff --git a/tests/QueryBuilder/DSL/SuggestTest.php b/tests/QueryBuilder/DSL/SuggestTest.php
index 4196026219..cc323d4772 100644
--- a/tests/QueryBuilder/DSL/SuggestTest.php
+++ b/tests/QueryBuilder/DSL/SuggestTest.php
@@ -5,12 +5,15 @@
 use Elastica\QueryBuilder\DSL;
 use Elastica\Suggest;
 
+/**
+ * @internal
+ */
 class SuggestTest extends AbstractDSLTest
 {
     /**
      * @group unit
      */
-    public function testType()
+    public function testType(): void
     {
         $suggestDSL = new DSL\Suggest();
 
@@ -21,7 +24,7 @@ public function testType()
     /**
      * @group unit
      */
-    public function testInterface()
+    public function testInterface(): void
     {
         $suggestDSL = new DSL\Suggest();
 
diff --git a/tests/QueryBuilder/VersionTest.php b/tests/QueryBuilder/VersionTest.php
index a1c3ad1800..7cd8272624 100644
--- a/tests/QueryBuilder/VersionTest.php
+++ b/tests/QueryBuilder/VersionTest.php
@@ -8,6 +8,8 @@
 
 /**
  * @group unit
+ *
+ * @internal
  */
 class VersionTest extends BaseTest
 {
diff --git a/tests/QueryBuilderTest.php b/tests/QueryBuilderTest.php
index a2b2c96ba5..ba0660e078 100644
--- a/tests/QueryBuilderTest.php
+++ b/tests/QueryBuilderTest.php
@@ -9,12 +9,15 @@
 use Elastica\QueryBuilder;
 use Elastica\Suggest\AbstractSuggest;
 
+/**
+ * @internal
+ */
 class QueryBuilderTest extends Base
 {
     /**
      * @group unit
      */
-    public function testCustomDSL()
+    public function testCustomDSL(): void
     {
         $qb = new QueryBuilder();
 
@@ -37,7 +40,7 @@ public function testCustomDSL()
     /**
      * @group unit
      */
-    public function testFacade()
+    public function testFacade(): void
     {
         $qb = new QueryBuilder();
 
diff --git a/tests/QueryTest.php b/tests/QueryTest.php
index 1e72cc0a92..c7241a619e 100644
--- a/tests/QueryTest.php
+++ b/tests/QueryTest.php
@@ -17,12 +17,15 @@
 use Elastica\Suggest;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class QueryTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testRawQuery()
+    public function testRawQuery(): void
     {
         $textQuery = new Term(['title' => 'test']);
 
@@ -37,7 +40,7 @@ public function testRawQuery()
     /**
      * @group unit
      */
-    public function testSuggestShouldNotRemoveOtherParameters()
+    public function testSuggestShouldNotRemoveOtherParameters(): void
     {
         $query1 = new Query();
         $query2 = new Query();
@@ -57,7 +60,7 @@ public function testSuggestShouldNotRemoveOtherParameters()
     /**
      * @group unit
      */
-    public function testSetSuggestMustReturnQueryInstance()
+    public function testSetSuggestMustReturnQueryInstance(): void
     {
         $query = new Query();
         $suggest = new Suggest();
@@ -67,7 +70,7 @@ public function testSetSuggestMustReturnQueryInstance()
     /**
      * @group unit
      */
-    public function testArrayQuery()
+    public function testArrayQuery(): void
     {
         $query = [
             'query' => [
@@ -88,7 +91,7 @@ public function testArrayQuery()
     /**
      * @group functional
      */
-    public function testSetSort()
+    public function testSetSort(): void
     {
         $index = $this->_createIndex();
         $index->setMapping(new Mapping([
@@ -135,7 +138,7 @@ public function testSetSort()
     /**
      * @group unit
      */
-    public function testAddSort()
+    public function testAddSort(): void
     {
         $query = new Query();
         $sortParam = ['firstname' => ['order' => 'asc']];
@@ -147,7 +150,7 @@ public function testAddSort()
     /**
      * @group unit
      */
-    public function testSetTrackScores()
+    public function testSetTrackScores(): void
     {
         $query = new Query();
         $param = false;
@@ -159,7 +162,7 @@ public function testSetTrackScores()
     /**
      * @group unit
      */
-    public function testSetRawQuery()
+    public function testSetRawQuery(): void
     {
         $query = new Query();
 
@@ -172,7 +175,7 @@ public function testSetRawQuery()
     /**
      * @group unit
      */
-    public function testSetStoredFields()
+    public function testSetStoredFields(): void
     {
         $query = new Query();
 
@@ -190,7 +193,7 @@ public function testSetStoredFields()
     /**
      * @group unit
      */
-    public function testGetQuery()
+    public function testGetQuery(): void
     {
         $query = new Query();
 
@@ -211,7 +214,7 @@ public function testGetQuery()
     /**
      * @group unit
      */
-    public function testSetQueryToArrayCast()
+    public function testSetQueryToArrayCast(): void
     {
         $query = new Query();
         $termQuery = new Term();
@@ -229,7 +232,7 @@ public function testSetQueryToArrayCast()
     /**
      * @group unit
      */
-    public function testNotCloneInnerObjects()
+    public function testNotCloneInnerObjects(): void
     {
         $query = new Query();
         $termQuery = new Term();
@@ -246,7 +249,7 @@ public function testNotCloneInnerObjects()
     /**
      * @group unit
      */
-    public function testSetQueryToArrayChangeQuery()
+    public function testSetQueryToArrayChangeQuery(): void
     {
         $query = new Query();
         $termQuery = new Term();
@@ -264,7 +267,7 @@ public function testSetQueryToArrayChangeQuery()
     /**
      * @group unit
      */
-    public function testSetScriptFieldsToArrayCast()
+    public function testSetScriptFieldsToArrayCast(): void
     {
         $query = new Query();
         $scriptFields = new ScriptFields();
@@ -283,7 +286,7 @@ public function testSetScriptFieldsToArrayCast()
     /**
      * @group unit
      */
-    public function testAddScriptFieldsToArrayCast()
+    public function testAddScriptFieldsToArrayCast(): void
     {
         $query = new Query();
         $scriptField = new Script('script');
@@ -301,7 +304,7 @@ public function testAddScriptFieldsToArrayCast()
     /**
      * @group unit
      */
-    public function testAddScriptFieldToExistingScriptFields()
+    public function testAddScriptFieldToExistingScriptFields(): void
     {
         $script1 = new Script('s1');
         $script2 = new Script('s2');
@@ -326,7 +329,7 @@ public function testAddScriptFieldToExistingScriptFields()
     /**
      * @group unit
      */
-    public function testAddAggregationToArrayCast()
+    public function testAddAggregationToArrayCast(): void
     {
         $query = new Query();
         $aggregation = new TermsAggregation('text');
@@ -345,7 +348,7 @@ public function testAddAggregationToArrayCast()
     /**
      * @group unit
      */
-    public function testSetSuggestToArrayCast()
+    public function testSetSuggestToArrayCast(): void
     {
         $query = new Query();
         $suggest = new Suggest();
@@ -364,7 +367,7 @@ public function testSetSuggestToArrayCast()
     /**
      * @group unit
      */
-    public function testSetRescoreToArrayCast()
+    public function testSetRescoreToArrayCast(): void
     {
         $query = new Query();
         $rescore = new RescoreQuery();
@@ -383,7 +386,7 @@ public function testSetRescoreToArrayCast()
     /**
      * @group unit
      */
-    public function testSetPostFilterToArrayCast()
+    public function testSetPostFilterToArrayCast(): void
     {
         $query = new Query();
         $postFilter = new Terms();
@@ -401,12 +404,13 @@ public function testSetPostFilterToArrayCast()
     /**
      * @group functional
      */
-    public function testNoSource()
+    public function testNoSource(): void
     {
         $index = $this->_createIndex();
 
         // Adds 1 document to the index
-        $doc1 = new Document(1,
+        $doc1 = new Document(
+            1,
             ['username' => 'ruflin', 'test' => ['2', '3', '5']]
         );
         $index->addDocument($doc1);
@@ -439,7 +443,7 @@ public function testNoSource()
     /**
      * @group unit
      */
-    public function testSetCollapseToArrayCast()
+    public function testSetCollapseToArrayCast(): void
     {
         $query = new Query();
         $collapse = new Collapse();
@@ -458,7 +462,7 @@ public function testSetCollapseToArrayCast()
     /**
      * @group unit
      */
-    public function testCollapseArrayStructure()
+    public function testCollapseArrayStructure(): void
     {
         $query = new Query();
         $collapse = new Collapse();
@@ -494,7 +498,7 @@ public function testCollapseArrayStructure()
     /**
      * @group unit
      */
-    public function testCollapseSecondLevelArrayStructure()
+    public function testCollapseSecondLevelArrayStructure(): void
     {
         $query = new Query();
         $collapse = new Collapse();
@@ -507,7 +511,7 @@ public function testCollapseSecondLevelArrayStructure()
                     ->setSort(['date' => 'asc'])
                     ->setCollapse(
                         (new Collapse())
-                        ->setFieldname('date')
+                            ->setFieldname('date')
                     )
             )
             ->setMaxConcurrentGroupSearches(4)
@@ -556,6 +560,8 @@ public function provideSetTrackTotalHitsInvalidValue(): iterable
     /**
      * @group functional
      * @dataProvider provideSetTrackTotalHitsInvalidValue
+     *
+     * @param mixed $value
      */
     public function testSetTrackTotalHitsInvalidValue($value): void
     {
diff --git a/tests/ReindexTest.php b/tests/ReindexTest.php
index 69a859f8e2..cedcd9cec9 100644
--- a/tests/ReindexTest.php
+++ b/tests/ReindexTest.php
@@ -12,12 +12,15 @@
 use Elastica\Reindex;
 use Elastica\Script\Script;
 
+/**
+ * @internal
+ */
 class ReindexTest extends Base
 {
     /**
      * @group functional
      */
-    public function testReindex()
+    public function testReindex(): void
     {
         $oldIndex = $this->_createIndex('idx1', true, 2);
         $this->_addDocs($oldIndex, 10);
@@ -35,7 +38,7 @@ public function testReindex()
     /**
      * @group functional
      */
-    public function testReindexOpTypeOptionWithProceedSetOnConflicts()
+    public function testReindexOpTypeOptionWithProceedSetOnConflicts(): void
     {
         $oldIndex = $this->_createIndex('idx1', true, 2);
         $docs1 = $this->_addDocs($oldIndex, 10);
@@ -62,7 +65,7 @@ public function testReindexOpTypeOptionWithProceedSetOnConflicts()
     /**
      * @group functional
      */
-    public function testReindexOpTypeOptionWithProceedSetOnConflictStop()
+    public function testReindexOpTypeOptionWithProceedSetOnConflictStop(): void
     {
         $oldIndex = $this->_createIndex('idx1', true, 2);
         $docs1 = $this->_addDocs($oldIndex, 10);
@@ -88,7 +91,7 @@ public function testReindexOpTypeOptionWithProceedSetOnConflictStop()
     /**
      * @group functional
      */
-    public function testReindexWithQueryOption()
+    public function testReindexWithQueryOption(): void
     {
         $oldIndex = $this->_createIndex('idx1', true, 2);
         $docs1 = $this->_addDocs($oldIndex, 10);
@@ -113,7 +116,7 @@ public function testReindexWithQueryOption()
     /**
      * @group functional
      */
-    public function testReindexWithSizeOption()
+    public function testReindexWithSizeOption(): void
     {
         $oldIndex = $this->_createIndex('idx1', true, 2);
         $this->_addDocs($oldIndex, 10);
@@ -132,7 +135,7 @@ public function testReindexWithSizeOption()
     /**
      * @group functional
      */
-    public function testReindexWithFalseSetOnWaitForCompletion()
+    public function testReindexWithFalseSetOnWaitForCompletion(): void
     {
         $oldIndex = $this->_createIndex('idx1', true, 2);
         $this->_addDocs($oldIndex, 10);
@@ -155,7 +158,7 @@ public function testReindexWithFalseSetOnWaitForCompletion()
     /**
      * @group functional
      */
-    public function testReindexWithScript()
+    public function testReindexWithScript(): void
     {
         $oldIndex = $this->_createIndex('idx1', true, 2);
         $this->_addDocs($oldIndex, 10);
@@ -181,7 +184,7 @@ public function testReindexWithScript()
     /**
      * @group functional
      */
-    public function testReindexWithRemote()
+    public function testReindexWithRemote(): void
     {
         $oldIndex = $this->_createIndex('idx1', true, 1);
         $newIndex = $this->_createIndex('idx2', true, 1);
diff --git a/tests/RequestTest.php b/tests/RequestTest.php
index 7e2e93a998..aa10c7418d 100644
--- a/tests/RequestTest.php
+++ b/tests/RequestTest.php
@@ -7,12 +7,15 @@
 use Elastica\Response;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class RequestTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testConstructor()
+    public function testConstructor(): void
     {
         $path = 'test';
         $method = Request::POST;
@@ -30,7 +33,7 @@ public function testConstructor()
     /**
      * @group unit
      */
-    public function testInvalidConnection()
+    public function testInvalidConnection(): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
 
@@ -41,7 +44,7 @@ public function testInvalidConnection()
     /**
      * @group functional
      */
-    public function testSend()
+    public function testSend(): void
     {
         $connection = new Connection();
         $connection->setHost($this->_getHost());
@@ -57,7 +60,7 @@ public function testSend()
     /**
      * @group unit
      */
-    public function testToString()
+    public function testToString(): void
     {
         $path = 'test';
         $method = Request::POST;
diff --git a/tests/ResponseFunctionalTest.php b/tests/ResponseFunctionalTest.php
index 9f9ab568fe..bdfc0b17d8 100644
--- a/tests/ResponseFunctionalTest.php
+++ b/tests/ResponseFunctionalTest.php
@@ -12,6 +12,8 @@
 
 /**
  * @group functional
+ *
+ * @internal
  */
 class ResponseFunctionalTest extends BaseTest
 {
diff --git a/tests/ResponseTest.php b/tests/ResponseTest.php
index b91edf37db..3ee6265875 100644
--- a/tests/ResponseTest.php
+++ b/tests/ResponseTest.php
@@ -7,6 +7,8 @@
 
 /**
  * @group unit
+ *
+ * @internal
  */
 class ResponseTest extends BaseTest
 {
diff --git a/tests/ResultSet/BuilderTest.php b/tests/ResultSet/BuilderTest.php
index b02e705167..d696b031dc 100644
--- a/tests/ResultSet/BuilderTest.php
+++ b/tests/ResultSet/BuilderTest.php
@@ -9,6 +9,8 @@
 
 /**
  * @group unit
+ *
+ * @internal
  */
 class BuilderTest extends BaseTest
 {
@@ -17,14 +19,14 @@ class BuilderTest extends BaseTest
      */
     private $builder;
 
-    protected function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
 
         $this->builder = new DefaultBuilder();
     }
 
-    public function testEmptyResponse()
+    public function testEmptyResponse(): void
     {
         $response = new Response('');
         $query = new Query();
@@ -36,7 +38,7 @@ public function testEmptyResponse()
         $this->assertCount(0, $resultSet->getResults());
     }
 
-    public function testResponse()
+    public function testResponse(): void
     {
         $response = new Response([
             'hits' => [
diff --git a/tests/ResultSet/ChainProcessorTest.php b/tests/ResultSet/ChainProcessorTest.php
index d8968453ad..15b270e809 100644
--- a/tests/ResultSet/ChainProcessorTest.php
+++ b/tests/ResultSet/ChainProcessorTest.php
@@ -11,10 +11,12 @@
 
 /**
  * @group unit
+ *
+ * @internal
  */
 class ChainProcessorTest extends BaseTest
 {
-    public function testProcessor()
+    public function testProcessor(): void
     {
         $processor = new ChainProcessor([
             $processor1 = $this->createMock(ProcessorInterface::class),
@@ -24,10 +26,12 @@ public function testProcessor()
 
         $processor1->expects($this->once())
             ->method('process')
-            ->with($resultSet);
+            ->with($resultSet)
+        ;
         $processor2->expects($this->once())
             ->method('process')
-            ->with($resultSet);
+            ->with($resultSet)
+        ;
 
         $processor->process($resultSet);
     }
diff --git a/tests/ResultSet/ProcessingBuilderTest.php b/tests/ResultSet/ProcessingBuilderTest.php
index 781dfd414f..4fd312cee8 100644
--- a/tests/ResultSet/ProcessingBuilderTest.php
+++ b/tests/ResultSet/ProcessingBuilderTest.php
@@ -12,6 +12,8 @@
 
 /**
  * @group unit
+ *
+ * @internal
  */
 class ProcessingBuilderTest extends BaseTest
 {
@@ -26,11 +28,11 @@ class ProcessingBuilderTest extends BaseTest
     private $innerBuilder;
 
     /**
-     * @var ProcessorInterface|PHPUnit_Framework_MockObject_MockObject
+     * @var PHPUnit_Framework_MockObject_MockObject|ProcessorInterface
      */
     private $processor;
 
-    protected function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
 
@@ -40,7 +42,7 @@ protected function setUp()
         $this->builder = new ProcessingBuilder($this->innerBuilder, $this->processor);
     }
 
-    public function testProcessors()
+    public function testProcessors(): void
     {
         $response = new Response('');
         $query = new Query();
@@ -49,10 +51,12 @@ public function testProcessors()
         $this->innerBuilder->expects($this->once())
             ->method('buildResultSet')
             ->with($response, $query)
-            ->willReturn($resultSet);
+            ->willReturn($resultSet)
+        ;
         $this->processor->expects($this->once())
             ->method('process')
-            ->with($resultSet);
+            ->with($resultSet)
+        ;
 
         $this->builder->buildResultSet($response, $query);
     }
diff --git a/tests/ResultSetTest.php b/tests/ResultSetTest.php
index 951f2b5901..76620d4137 100644
--- a/tests/ResultSetTest.php
+++ b/tests/ResultSetTest.php
@@ -8,12 +8,15 @@
 use Elastica\ResultSet;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class ResultSetTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testGetters()
+    public function testGetters(): void
     {
         $index = $this->_createIndex();
         $index->addDocuments([
@@ -39,7 +42,7 @@ public function testGetters()
     /**
      * @group functional
      */
-    public function testArrayAccess()
+    public function testArrayAccess(): void
     {
         $index = $this->_createIndex();
         $index->addDocuments([
@@ -62,7 +65,7 @@ public function testArrayAccess()
     /**
      * @group functional
      */
-    public function testDocumentsAccess()
+    public function testDocumentsAccess(): void
     {
         $index = $this->_createIndex();
         $index->addDocuments([
@@ -90,7 +93,7 @@ public function testDocumentsAccess()
     /**
      * @group functional
      */
-    public function testInvalidOffsetCreation()
+    public function testInvalidOffsetCreation(): void
     {
         $this->expectException(InvalidException::class);
 
diff --git a/tests/ResultTest.php b/tests/ResultTest.php
index ff96a928c9..86c49e63b1 100644
--- a/tests/ResultTest.php
+++ b/tests/ResultTest.php
@@ -7,12 +7,15 @@
 use Elastica\Result;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class ResultTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testGetters()
+    public function testGetters(): void
     {
         // Creates a new index 'xodoa'
         $index = $this->_createIndex();
@@ -38,7 +41,7 @@ public function testGetters()
     /**
      * @group functional
      */
-    public function testGetIdNoSource()
+    public function testGetIdNoSource(): void
     {
         // Creates a new index 'xodoa'
         $indexName = 'xodoa';
@@ -76,7 +79,7 @@ public function testGetIdNoSource()
     /**
      * @group functional
      */
-    public function testGetTotalTimeReturnsExpectedResults()
+    public function testGetTotalTimeReturnsExpectedResults(): void
     {
         $index = $this->_createIndex();
 
@@ -95,13 +98,13 @@ public function testGetTotalTimeReturnsExpectedResults()
             'integer',
             \gettype($resultSet->getTotalTime()),
             'Total Time should be an integer'
-         );
+        );
     }
 
     /**
      * @group unit
      */
-    public function testHasFields()
+    public function testHasFields(): void
     {
         $data = ['value set'];
 
diff --git a/tests/Script/ScriptFieldsTest.php b/tests/Script/ScriptFieldsTest.php
index 079ff9cfb4..7d14a974e0 100644
--- a/tests/Script/ScriptFieldsTest.php
+++ b/tests/Script/ScriptFieldsTest.php
@@ -8,12 +8,15 @@
 use Elastica\Script\ScriptFields;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class ScriptFieldsTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testNewScriptFields()
+    public function testNewScriptFields(): void
     {
         $script = new Script('1 + 2');
 
@@ -39,7 +42,7 @@ public function testNewScriptFields()
     /**
      * @group unit
      */
-    public function testSetScriptFields()
+    public function testSetScriptFields(): void
     {
         $query = new Query();
         $script = new Script('1 + 2');
@@ -59,7 +62,7 @@ public function testSetScriptFields()
     /**
      * @group functional
      */
-    public function testQuery()
+    public function testQuery(): void
     {
         $index = $this->_createIndex();
 
@@ -84,7 +87,7 @@ public function testQuery()
     /**
      * @group functional
      */
-    public function testScriptFieldWithJoin()
+    public function testScriptFieldWithJoin(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('testscriptfieldwithjoin');
diff --git a/tests/Script/ScriptIdTest.php b/tests/Script/ScriptIdTest.php
index d59e1c4fec..da6b2601a9 100644
--- a/tests/Script/ScriptIdTest.php
+++ b/tests/Script/ScriptIdTest.php
@@ -5,6 +5,9 @@
 use Elastica\Script\ScriptId;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class ScriptIdTest extends BaseTest
 {
     private const SCRIPT_ID = 'my_script';
@@ -12,7 +15,7 @@ class ScriptIdTest extends BaseTest
     /**
      * @group unit
      */
-    public function testConstructor()
+    public function testConstructor(): void
     {
         $script = new ScriptId(self::SCRIPT_ID);
 
@@ -55,7 +58,7 @@ public function testConstructor()
     /**
      * @group unit
      */
-    public function testCreateString()
+    public function testCreateString(): void
     {
         $script = ScriptId::create(self::SCRIPT_ID);
 
@@ -72,7 +75,7 @@ public function testCreateString()
     /**
      * @group unit
      */
-    public function testCreateScript()
+    public function testCreateScript(): void
     {
         $data = new ScriptId(self::SCRIPT_ID);
 
@@ -85,7 +88,7 @@ public function testCreateScript()
     /**
      * @group unit
      */
-    public function testCreateArray()
+    public function testCreateArray(): void
     {
         $params = [
             'param1' => 'one',
@@ -112,8 +115,10 @@ public function testCreateArray()
     /**
      * @group unit
      * @dataProvider dataProviderCreateInvalid
+     *
+     * @param mixed $data
      */
-    public function testCreateInvalid($data)
+    public function testCreateInvalid($data): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
 
@@ -141,7 +146,7 @@ public function dataProviderCreateInvalid()
     /**
      * @group unit
      */
-    public function testSetLang()
+    public function testSetLang(): void
     {
         $script = new ScriptId(self::SCRIPT_ID, [], ScriptId::LANG_PAINLESS);
 
@@ -152,7 +157,7 @@ public function testSetLang()
     /**
      * @group unit
      */
-    public function testSetScriptId()
+    public function testSetScriptId(): void
     {
         $script = new ScriptId(self::SCRIPT_ID);
 
diff --git a/tests/Script/ScriptTest.php b/tests/Script/ScriptTest.php
index 7569a8e2a4..4bd0400977 100644
--- a/tests/Script/ScriptTest.php
+++ b/tests/Script/ScriptTest.php
@@ -5,6 +5,9 @@
 use Elastica\Script\Script;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class ScriptTest extends BaseTest
 {
     private const SCRIPT = "_score * doc['my_numeric_field'].value";
@@ -12,7 +15,7 @@ class ScriptTest extends BaseTest
     /**
      * @group unit
      */
-    public function testConstructor()
+    public function testConstructor(): void
     {
         $script = new Script(self::SCRIPT);
 
@@ -55,7 +58,7 @@ public function testConstructor()
     /**
      * @group unit
      */
-    public function testCreateString()
+    public function testCreateString(): void
     {
         $script = Script::create(self::SCRIPT);
 
@@ -72,7 +75,7 @@ public function testCreateString()
     /**
      * @group unit
      */
-    public function testCreateScript()
+    public function testCreateScript(): void
     {
         $data = new Script(self::SCRIPT);
 
@@ -85,7 +88,7 @@ public function testCreateScript()
     /**
      * @group unit
      */
-    public function testCreateArray()
+    public function testCreateArray(): void
     {
         $params = [
             'param1' => 'one',
@@ -112,8 +115,10 @@ public function testCreateArray()
     /**
      * @group unit
      * @dataProvider dataProviderCreateInvalid
+     *
+     * @param mixed $data
      */
-    public function testCreateInvalid($data)
+    public function testCreateInvalid($data): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
 
@@ -141,7 +146,7 @@ public function dataProviderCreateInvalid()
     /**
      * @group unit
      */
-    public function testSetLang()
+    public function testSetLang(): void
     {
         $script = new Script(self::SCRIPT, [], Script::LANG_PAINLESS);
 
@@ -152,7 +157,7 @@ public function testSetLang()
     /**
      * @group unit
      */
-    public function testSetScript()
+    public function testSetScript(): void
     {
         $script = new Script(self::SCRIPT);
 
diff --git a/tests/ScrollTest.php b/tests/ScrollTest.php
index 8cb8fff2f9..38597a6c1b 100644
--- a/tests/ScrollTest.php
+++ b/tests/ScrollTest.php
@@ -8,6 +8,9 @@
 use Elastica\Scroll;
 use Elastica\Search;
 
+/**
+ * @internal
+ */
 class ScrollTest extends Base
 {
     /**
@@ -15,7 +18,7 @@ class ScrollTest extends Base
      *
      * @group functional
      */
-    public function testForeach()
+    public function testForeach(): void
     {
         $search = $this->_prepareSearch();
         $scroll = new Scroll($search);
@@ -62,7 +65,7 @@ public function testForeach()
      *
      * @group functional
      */
-    public function testSearchRevert()
+    public function testSearchRevert(): void
     {
         $search = $this->_prepareSearch();
 
@@ -84,7 +87,7 @@ public function testSearchRevert()
      *
      * @group functional
      */
-    public function testEmptyScroll()
+    public function testEmptyScroll(): void
     {
         $search = $this->_prepareSearch(0);
         $scroll = new Scroll($search);
@@ -104,7 +107,7 @@ public function testEmptyScroll()
      *
      * @group functional
      */
-    public function testScrollWithIgnoreUnavailable()
+    public function testScrollWithIgnoreUnavailable(): void
     {
         $search = $this->_prepareSearch();
         $search->addIndex('unavailable_index');
@@ -176,7 +179,7 @@ private function _prepareSearch(int $indexSize = 11): Search
     /**
      * Tests the number of open search contexts on ES.
      */
-    private function _assertOpenSearchContexts(Client $client, int $count)
+    private function _assertOpenSearchContexts(Client $client, int $count): void
     {
         $stats = $client->getStatus()->getData();
         $this->assertSame($count, $stats['_all']['total']['search']['open_contexts'], 'Open search contexts should match');
diff --git a/tests/SearchTest.php b/tests/SearchTest.php
index 4f5b4342e9..120ffe8e50 100644
--- a/tests/SearchTest.php
+++ b/tests/SearchTest.php
@@ -19,12 +19,15 @@
 use Elastica\Suggest;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class SearchTest extends BaseTest
 {
     /**
      * @group unit
      */
-    public function testConstruct()
+    public function testConstruct(): void
     {
         $client = $this->_getClient();
         $search = new Search($client);
@@ -35,7 +38,7 @@ public function testConstruct()
     /**
      * @group functional
      */
-    public function testAddIndex()
+    public function testAddIndex(): void
     {
         $client = $this->_getClient();
         $search = new Search($client);
@@ -67,7 +70,7 @@ public function testAddIndex()
     /**
      * @group unit
      */
-    public function testAddIndices()
+    public function testAddIndices(): void
     {
         $client = $this->_getClient();
         $search = new Search($client);
@@ -84,7 +87,7 @@ public function testAddIndices()
     /**
      * @group unit
      */
-    public function testAddIndexInvalid()
+    public function testAddIndexInvalid(): void
     {
         $this->expectException(InvalidException::class);
 
@@ -97,7 +100,7 @@ public function testAddIndexInvalid()
     /**
      * @group unit
      */
-    public function testAddNumericIndex()
+    public function testAddNumericIndex(): void
     {
         $client = $this->_getClient();
         $search = new Search($client);
@@ -110,7 +113,7 @@ public function testAddNumericIndex()
     /**
      * @group functional
      */
-    public function testGetPath()
+    public function testGetPath(): void
     {
         $client = $this->_getClient();
         $search1 = new Search($client);
@@ -133,7 +136,7 @@ public function testGetPath()
     /**
      * @group functional
      */
-    public function testSearchRequest()
+    public function testSearchRequest(): void
     {
         $client = $this->_getClient();
         $search1 = new Search($client);
@@ -154,7 +157,7 @@ public function testSearchRequest()
     /**
      * @group functional
      */
-    public function testSearchScrollRequest()
+    public function testSearchScrollRequest(): void
     {
         $client = $this->_getClient();
 
@@ -209,7 +212,7 @@ public function testSearchScrollRequest()
      *
      * @group functional
      */
-    public function testLimitDefaultSearch()
+    public function testLimitDefaultSearch(): void
     {
         $client = $this->_getClient();
         $search = new Search($client);
@@ -246,7 +249,7 @@ public function testLimitDefaultSearch()
     /**
      * @group functional
      */
-    public function testArrayConfigSearch()
+    public function testArrayConfigSearch(): void
     {
         $client = $this->_getClient();
         $search = new Search($client);
@@ -310,7 +313,8 @@ public function testArrayConfigSearch()
         $suggestName = new Suggest((new Suggest\Term('name_suggest', 'username'))->setText('tes'));
         $typedKeysQuery = (new Query())
             ->addAggregation($countIds)
-            ->setSuggest($suggestName);
+            ->setSuggest($suggestName)
+        ;
         $resultSet = $search->search($typedKeysQuery, [Search::OPTION_TYPED_KEYS => true]);
         $this->assertNotEmpty($resultSet->getAggregation('cardinality#count_ids'));
         $this->assertNotEmpty($resultSet->getSuggests(), 'term#name_suggest');
@@ -319,7 +323,8 @@ public function testArrayConfigSearch()
         $mockResponse = new Response(\json_encode(['timed_out' => true]));
         $client = $this->createMock(Client::class);
         $client->method('request')
-            ->will($this->returnValue($mockResponse));
+            ->will($this->returnValue($mockResponse))
+        ;
         $search = new Search($client);
         $script = new Script('Thread.sleep(100); return _score;');
         $query = new FunctionScore();
@@ -331,7 +336,7 @@ public function testArrayConfigSearch()
     /**
      * @group functional
      */
-    public function testInvalidConfigSearch()
+    public function testInvalidConfigSearch(): void
     {
         $this->expectException(InvalidException::class);
 
@@ -344,7 +349,7 @@ public function testInvalidConfigSearch()
     /**
      * @group functional
      */
-    public function testSearchWithVersionOption()
+    public function testSearchWithVersionOption(): void
     {
         $index = $this->_createIndex();
         $doc = new Document(1, ['id' => 1, 'email' => 'test@test.com', 'username' => 'ruflin']);
@@ -368,7 +373,7 @@ public function testSearchWithVersionOption()
     /**
      * @group functional
      */
-    public function testSearchGet()
+    public function testSearchGet(): void
     {
         $client = $this->_getClient();
         $search1 = new Search($client);
@@ -380,7 +385,7 @@ public function testSearchGet()
     /**
      * @group functional
      */
-    public function testCountRequest()
+    public function testCountRequest(): void
     {
         $client = $this->_getClient();
         $search = new Search($client);
@@ -424,7 +429,7 @@ public function testCountRequest()
     /**
      * @group functional
      */
-    public function testCountRequestGet()
+    public function testCountRequestGet(): void
     {
         $client = $this->_getClient();
         $search = new Search($client);
@@ -468,7 +473,7 @@ public function testCountRequestGet()
     /**
      * @group functional
      */
-    public function testEmptySearch()
+    public function testEmptySearch(): void
     {
         $client = $this->_getClient();
         $search = new Search($client);
@@ -510,7 +515,7 @@ public function testEmptySearch()
     /**
      * @group functional
      */
-    public function testCount()
+    public function testCount(): void
     {
         $index = $this->_createIndex();
         $search = new Search($index->getClient());
@@ -533,7 +538,7 @@ public function testCount()
     /**
      * @group functional
      */
-    public function testIgnoreUnavailableOption()
+    public function testIgnoreUnavailableOption(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('elastica_7086b4c2ee585bbb6740ece5ed7ece01');
@@ -560,7 +565,7 @@ public function testIgnoreUnavailableOption()
     /**
      * @group functional
      */
-    public function testQuerySizeAfterCount()
+    public function testQuerySizeAfterCount(): void
     {
         $client = $this->_getClient();
         $search = new Search($client);
diff --git a/tests/SnapshotTest.php b/tests/SnapshotTest.php
index e8614d3b9e..4c17c07f33 100644
--- a/tests/SnapshotTest.php
+++ b/tests/SnapshotTest.php
@@ -9,6 +9,8 @@
 
 /**
  * @group functional
+ *
+ * @internal
  */
 class SnapshotTest extends Base
 {
@@ -30,7 +32,7 @@ class SnapshotTest extends Base
      */
     protected $docs;
 
-    protected function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
         $this->snapshot = new Snapshot($this->_getClient());
diff --git a/tests/StatusTest.php b/tests/StatusTest.php
index 08f5fcac39..88d0a80910 100644
--- a/tests/StatusTest.php
+++ b/tests/StatusTest.php
@@ -7,12 +7,15 @@
 use Elastica\Status;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class StatusTest extends BaseTest
 {
     /**
      * @group functional
      */
-    public function testGetResponse()
+    public function testGetResponse(): void
     {
         $index = $this->_createIndex();
         $status = new Status($index->getClient());
@@ -22,7 +25,7 @@ public function testGetResponse()
     /**
      * @group functional
      */
-    public function testGetIndexNames()
+    public function testGetIndexNames(): void
     {
         $indexName = 'test';
         $client = $this->_getClient();
@@ -46,7 +49,7 @@ public function testGetIndexNames()
     /**
      * @group functional
      */
-    public function testIndexExists()
+    public function testIndexExists(): void
     {
         $indexName = 'elastica_test';
         $aliasName = 'elastica_test-alias';
@@ -72,7 +75,7 @@ public function testIndexExists()
     /**
      * @group functional
      */
-    public function testAliasExists()
+    public function testAliasExists(): void
     {
         $aliasName = 'elastica_test-alias';
 
@@ -95,6 +98,8 @@ public function testAliasExists()
         $this->assertEquals([$indexName], \array_map(
             function ($index) {
                 return $index->getName();
-            }, $indicesWithAlias));
+            },
+            $indicesWithAlias
+        ));
     }
 }
diff --git a/tests/Suggest/CompletionTest.php b/tests/Suggest/CompletionTest.php
index cc636f6998..12e21d0e39 100644
--- a/tests/Suggest/CompletionTest.php
+++ b/tests/Suggest/CompletionTest.php
@@ -10,65 +10,15 @@
 use Elastica\Suggest\Completion;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class CompletionTest extends BaseTest
 {
-    /**
-     * @return Index
-     */
-    protected function _getIndexForTest()
-    {
-        $index = $this->_createIndex();
-        $index->setMapping(new Mapping([
-            'fieldName' => [
-                'type' => 'completion',
-            ],
-            'fieldName2' => [
-                'type' => 'completion',
-            ],
-        ]));
-
-        $index->addDocuments([
-            new Document(1, [
-                'fieldName' => [
-                    'input' => ['Nevermind', 'Nirvana'],
-                    'weight' => 5,
-                ],
-            ]),
-            new Document(2, [
-                'fieldName' => [
-                    'input' => ['Bleach', 'Nirvana'],
-                    'weight' => 2,
-                ],
-            ]),
-            new Document(3, [
-                'fieldName' => [
-                    'input' => ['Incesticide', 'Nirvana'],
-                    'weight' => 7,
-                ],
-            ]),
-            new Document(4, [
-                'fieldName2' => [
-                    'input' => ['Bleach', 'Nirvana'],
-                    'weight' => 3,
-                ],
-            ]),
-            new Document(5, [
-                'fieldName2' => [
-                    'input' => ['Incesticide', 'Nirvana'],
-                    'weight' => 3,
-                ],
-            ]),
-        ]);
-
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $suggest = new Completion('suggestName', 'fieldName');
         $suggest->setPrefix('foo');
@@ -86,7 +36,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testSuggestWorks()
+    public function testSuggestWorks(): void
     {
         $suggest = new Completion('suggestName', 'fieldName');
         $suggest->setPrefix('Never');
@@ -106,7 +56,7 @@ public function testSuggestWorks()
     /**
      * @group functional
      */
-    public function testFuzzySuggestWorks()
+    public function testFuzzySuggestWorks(): void
     {
         $suggest = new Completion('suggestName', 'fieldName');
         $suggest->setFuzzy(['fuzziness' => 2]);
@@ -127,7 +77,7 @@ public function testFuzzySuggestWorks()
     /**
      * @group functional
      */
-    public function testCompletion()
+    public function testCompletion(): void
     {
         $suggest = new Completion('suggestName1', 'fieldName');
         $suggest->setPrefix('Neavermint');
@@ -142,21 +92,21 @@ public function testCompletion()
         $query = Query::create($sug);
 
         $expectedSuggestions = [
-          'suggestName1' => [
-              0 => [
-                  'text' => 'Neavermint',
-                  'offset' => 0,
-                  'length' => 10,
-                  'options' => [],
-                  ],
-          ],
+            'suggestName1' => [
+                0 => [
+                    'text' => 'Neavermint',
+                    'offset' => 0,
+                    'length' => 10,
+                    'options' => [],
+                ],
+            ],
             'suggestName2' => [
                 0 => [
                     'text' => 'Neverdint',
                     'offset' => 0,
                     'length' => 9,
                     'options' => [],
-                    ],
+                ],
             ],
         ];
 
@@ -169,7 +119,7 @@ public function testCompletion()
     /**
      * @group unit
      */
-    public function testSetFuzzy()
+    public function testSetFuzzy(): void
     {
         $suggest = new Completion('suggestName', 'fieldName');
 
@@ -188,7 +138,7 @@ public function testSetFuzzy()
     /**
      * @group functional
      */
-    public function testRegexSuggestWorks()
+    public function testRegexSuggestWorks(): void
     {
         $suggest = new Completion('suggestName', 'fieldName');
         $suggest->setRegex('n[ever|i]r');
@@ -200,4 +150,57 @@ public function testRegexSuggestWorks()
         $options = $suggests['suggestName'][0]['options'];
         $this->assertCount(3, $options);
     }
+
+    /**
+     * @return Index
+     */
+    protected function _getIndexForTest()
+    {
+        $index = $this->_createIndex();
+        $index->setMapping(new Mapping([
+            'fieldName' => [
+                'type' => 'completion',
+            ],
+            'fieldName2' => [
+                'type' => 'completion',
+            ],
+        ]));
+
+        $index->addDocuments([
+            new Document(1, [
+                'fieldName' => [
+                    'input' => ['Nevermind', 'Nirvana'],
+                    'weight' => 5,
+                ],
+            ]),
+            new Document(2, [
+                'fieldName' => [
+                    'input' => ['Bleach', 'Nirvana'],
+                    'weight' => 2,
+                ],
+            ]),
+            new Document(3, [
+                'fieldName' => [
+                    'input' => ['Incesticide', 'Nirvana'],
+                    'weight' => 7,
+                ],
+            ]),
+            new Document(4, [
+                'fieldName2' => [
+                    'input' => ['Bleach', 'Nirvana'],
+                    'weight' => 3,
+                ],
+            ]),
+            new Document(5, [
+                'fieldName2' => [
+                    'input' => ['Incesticide', 'Nirvana'],
+                    'weight' => 3,
+                ],
+            ]),
+        ]);
+
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Suggest/PhraseTest.php b/tests/Suggest/PhraseTest.php
index 1aeed56408..cb13a7663b 100644
--- a/tests/Suggest/PhraseTest.php
+++ b/tests/Suggest/PhraseTest.php
@@ -9,30 +9,15 @@
 use Elastica\Suggest\Phrase;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class PhraseTest extends BaseTest
 {
-    /**
-     * @return Index
-     */
-    protected function _getIndexForTest()
-    {
-        $index = $this->_createIndex();
-        $index->addDocuments([
-            new Document(1, ['text' => 'Github is pretty cool']),
-            new Document(2, ['text' => 'Elasticsearch is bonsai cool']),
-            new Document(3, ['text' => 'This is a test phrase']),
-            new Document(4, ['text' => 'Another sentence for testing']),
-            new Document(5, ['text' => 'Some more words here']),
-        ]);
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $suggest = new Suggest();
         $phraseSuggest = new Phrase('suggest1', 'text');
@@ -60,7 +45,7 @@ public function testToArray()
     /**
      * @group functional
      */
-    public function testPhraseSuggest()
+    public function testPhraseSuggest(): void
     {
         $suggest = new Suggest();
         $phraseSuggest = new Phrase('suggest1', 'text');
@@ -79,4 +64,22 @@ public function testPhraseSuggest()
         $this->assertEquals('elasticsearch is <suggest>bonsai cool</suggest>', $suggests['suggest1'][0]['options'][0]['highlighted']);
         $this->assertEquals('elasticsearch is bonsai cool', $suggests['suggest1'][0]['options'][0]['text']);
     }
+
+    /**
+     * @return Index
+     */
+    protected function _getIndexForTest()
+    {
+        $index = $this->_createIndex();
+        $index->addDocuments([
+            new Document(1, ['text' => 'Github is pretty cool']),
+            new Document(2, ['text' => 'Elasticsearch is bonsai cool']),
+            new Document(3, ['text' => 'This is a test phrase']),
+            new Document(4, ['text' => 'Another sentence for testing']),
+            new Document(5, ['text' => 'Some more words here']),
+        ]);
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/Suggest/TermTest.php b/tests/Suggest/TermTest.php
index ed128f2823..29a379b232 100644
--- a/tests/Suggest/TermTest.php
+++ b/tests/Suggest/TermTest.php
@@ -8,31 +8,15 @@
 use Elastica\Suggest\Term;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class TermTest extends BaseTest
 {
-    /**
-     * @return Index
-     */
-    protected function _getIndexForTest()
-    {
-        $index = $this->_createIndex();
-        $index->addDocuments([
-            new Document(1, ['id' => 1, 'text' => 'GitHub']),
-            new Document(2, ['id' => 1, 'text' => 'Elastic']),
-            new Document(3, ['id' => 1, 'text' => 'Search']),
-            new Document(4, ['id' => 1, 'text' => 'Food']),
-            new Document(5, ['id' => 1, 'text' => 'Flood']),
-            new Document(6, ['id' => 1, 'text' => 'Folks']),
-        ]);
-        $index->refresh();
-
-        return $index;
-    }
-
     /**
      * @group unit
      */
-    public function testToArray()
+    public function testToArray(): void
     {
         $suggest = new Suggest();
 
@@ -70,7 +54,7 @@ public function testToArray()
     /**
      * @group unit
      */
-    public function testDistanceAlgorithm()
+    public function testDistanceAlgorithm(): void
     {
         $suggest = new Suggest();
 
@@ -110,7 +94,7 @@ public function testDistanceAlgorithm()
     /**
      * @group functional
      */
-    public function testSuggestResults()
+    public function testSuggestResults(): void
     {
         $suggest = new Suggest();
         $suggest1 = new Term('suggest1', 'text');
@@ -136,7 +120,7 @@ public function testSuggestResults()
     /**
      * @group functional
      */
-    public function testSuggestNoResults()
+    public function testSuggestNoResults(): void
     {
         $termSuggest = new Term('suggest1', 'text');
         $termSuggest->setText('Foobar')->setSize(4);
@@ -150,4 +134,23 @@ public function testSuggestNoResults()
         $suggests = $result->getSuggests();
         $this->assertCount(0, $suggests['suggest1'][0]['options']);
     }
+
+    /**
+     * @return Index
+     */
+    protected function _getIndexForTest()
+    {
+        $index = $this->_createIndex();
+        $index->addDocuments([
+            new Document(1, ['id' => 1, 'text' => 'GitHub']),
+            new Document(2, ['id' => 1, 'text' => 'Elastic']),
+            new Document(3, ['id' => 1, 'text' => 'Search']),
+            new Document(4, ['id' => 1, 'text' => 'Food']),
+            new Document(5, ['id' => 1, 'text' => 'Flood']),
+            new Document(6, ['id' => 1, 'text' => 'Folks']),
+        ]);
+        $index->refresh();
+
+        return $index;
+    }
 }
diff --git a/tests/SuggestTest.php b/tests/SuggestTest.php
index b559877cb1..5e50bebe06 100644
--- a/tests/SuggestTest.php
+++ b/tests/SuggestTest.php
@@ -8,6 +8,9 @@
 use Elastica\Suggest\Term;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class SuggestTest extends BaseTest
 {
     /**
@@ -15,7 +18,7 @@ class SuggestTest extends BaseTest
      *
      * @group functional
      */
-    public function testCreateSelf()
+    public function testCreateSelf(): void
     {
         $suggest = new Suggest();
 
@@ -29,7 +32,7 @@ public function testCreateSelf()
      *
      * @group functional
      */
-    public function testCreateWithSuggest()
+    public function testCreateWithSuggest(): void
     {
         $suggest1 = new Term('suggest1', '_all');
 
@@ -43,7 +46,7 @@ public function testCreateWithSuggest()
      *
      * @group functional
      */
-    public function testCreateWithNonSuggest()
+    public function testCreateWithNonSuggest(): void
     {
         try {
             Suggest::create(new BoolQuery());
diff --git a/tests/TaskTest.php b/tests/TaskTest.php
index 88b80b6f61..973e4ccb81 100644
--- a/tests/TaskTest.php
+++ b/tests/TaskTest.php
@@ -5,12 +5,15 @@
 use Elastica\Document;
 use Elastica\Task;
 
+/**
+ * @internal
+ */
 class TaskTest extends Base
 {
     /**
      * @group functional
      */
-    public function testGetData()
+    public function testGetData(): void
     {
         $task = $this->_createTask();
         $data = $task->getData();
@@ -22,7 +25,7 @@ public function testGetData()
     /**
      * @group functional
      */
-    public function testGetId()
+    public function testGetId(): void
     {
         $task = $this->_createTask();
         $data = $task->getData();
@@ -34,7 +37,7 @@ public function testGetId()
     /**
      * @group functional
      */
-    public function testIsComplete()
+    public function testIsComplete(): void
     {
         $task = $this->_createTask();
 
@@ -52,7 +55,7 @@ public function testIsComplete()
     /**
      * @group functional
      */
-    public function testRefreshWithOptionsContainingOnWaitForResponseTrue()
+    public function testRefreshWithOptionsContainingOnWaitForResponseTrue(): void
     {
         $task = $this->_createTask();
         $task->refresh([Task::WAIT_FOR_COMPLETION => Task::WAIT_FOR_COMPLETION_TRUE]);
@@ -62,7 +65,7 @@ public function testRefreshWithOptionsContainingOnWaitForResponseTrue()
     /**
      * @group unit
      */
-    public function testCancelThrowsExceptionWithEmptyTaskId()
+    public function testCancelThrowsExceptionWithEmptyTaskId(): void
     {
         $this->expectException(\Exception::class);
         $this->expectExceptionMessage('No task id given');
@@ -74,7 +77,7 @@ public function testCancelThrowsExceptionWithEmptyTaskId()
     /**
      * @group functional
      */
-    public function testCancelDoesntCancelCompletedTasks()
+    public function testCancelDoesntCancelCompletedTasks(): void
     {
         $task = $this->_createTask();
         $task->refresh([Task::WAIT_FOR_COMPLETION => Task::WAIT_FOR_COMPLETION_TRUE]);
diff --git a/tests/Transport/AbstractTransportTest.php b/tests/Transport/AbstractTransportTest.php
index 31afd3a29e..607f36eef8 100644
--- a/tests/Transport/AbstractTransportTest.php
+++ b/tests/Transport/AbstractTransportTest.php
@@ -10,6 +10,9 @@
 use Elastica\Transport\AbstractTransport;
 use Elastica\Transport\Http;
 
+/**
+ * @internal
+ */
 class AbstractTransportTest extends BaseTest
 {
     /**
@@ -50,8 +53,10 @@ public function getValidDefinitions()
     /**
      * @group unit
      * @dataProvider getValidDefinitions
+     *
+     * @param mixed $transport
      */
-    public function testCanCreateTransportInstances($transport)
+    public function testCanCreateTransportInstances($transport): void
     {
         $connection = new Connection();
         $params = [];
@@ -71,8 +76,10 @@ public function getInvalidDefinitions()
     /**
      * @group unit
      * @dataProvider getInvalidDefinitions
+     *
+     * @param mixed $transport
      */
-    public function testThrowsExecptionOnInvalidTransportDefinition($transport)
+    public function testThrowsExecptionOnInvalidTransportDefinition($transport): void
     {
         $this->expectException(\Elastica\Exception\InvalidException::class);
         $this->expectExceptionMessage('Invalid transport');
@@ -83,7 +90,7 @@ public function testThrowsExecptionOnInvalidTransportDefinition($transport)
     /**
      * @group unit
      */
-    public function testCanInjectParamsWhenUsingArray()
+    public function testCanInjectParamsWhenUsingArray(): void
     {
         $connection = new Connection();
         $params = [
@@ -109,8 +116,10 @@ public function testCanInjectParamsWhenUsingArray()
      *
      * @group functional
      * @dataProvider getTransport
+     *
+     * @param mixed $transport
      */
-    public function testBooleanStringValues($transport)
+    public function testBooleanStringValues($transport): void
     {
         $client = $this->_getClient($transport);
         $index = $client->getIndex('elastica_testbooleanstringvalues');
diff --git a/tests/Transport/AwsAuthV4Test.php b/tests/Transport/AwsAuthV4Test.php
index 6ae409ae0e..6f70911c0f 100644
--- a/tests/Transport/AwsAuthV4Test.php
+++ b/tests/Transport/AwsAuthV4Test.php
@@ -7,9 +7,12 @@
 use Elastica\Exception\Connection\GuzzleException;
 use GuzzleHttp\Exception\RequestException;
 
+/**
+ * @internal
+ */
 class AwsAuthV4Test extends GuzzleTest
 {
-    public static function setUpBeforeClass()
+    public static function setUpBeforeClass(): void
     {
         if (!\class_exists('Aws\\Sdk')) {
             self::markTestSkipped('aws/aws-sdk-php package should be installed to run SignatureV4 transport tests');
@@ -19,7 +22,7 @@ public static function setUpBeforeClass()
     /**
      * @group unit
      */
-    public function testSignsWithProvidedCredentialProvider()
+    public function testSignsWithProvidedCredentialProvider(): void
     {
         $config = [
             'persistent' => false,
@@ -57,7 +60,7 @@ public function testSignsWithProvidedCredentialProvider()
     /**
      * @group unit
      */
-    public function testPrefersCredentialProviderToHardCodedCredentials()
+    public function testPrefersCredentialProviderToHardCodedCredentials(): void
     {
         $config = [
             'persistent' => false,
@@ -98,7 +101,7 @@ public function testPrefersCredentialProviderToHardCodedCredentials()
     /**
      * @group unit
      */
-    public function testSignsWithProvidedCredentials()
+    public function testSignsWithProvidedCredentials(): void
     {
         $config = [
             'persistent' => false,
@@ -133,7 +136,7 @@ public function testSignsWithProvidedCredentials()
         }
     }
 
-    public function testUseHttpAsDefaultProtocol()
+    public function testUseHttpAsDefaultProtocol(): void
     {
         $config = [
             'persistent' => false,
@@ -157,7 +160,7 @@ public function testUseHttpAsDefaultProtocol()
         }
     }
 
-    public function testSetHttpsIfItIsRequired()
+    public function testSetHttpsIfItIsRequired(): void
     {
         $config = [
             'persistent' => false,
@@ -182,7 +185,7 @@ public function testSetHttpsIfItIsRequired()
         }
     }
 
-    public function testSignsWithEnvironmentalCredentials()
+    public function testSignsWithEnvironmentalCredentials(): void
     {
         $config = [
             'persistent' => false,
diff --git a/tests/Transport/GuzzleTest.php b/tests/Transport/GuzzleTest.php
index 90a1a461b1..962cca542f 100644
--- a/tests/Transport/GuzzleTest.php
+++ b/tests/Transport/GuzzleTest.php
@@ -7,19 +7,33 @@
 use Elastica\ResultSet\DefaultBuilder;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class GuzzleTest extends BaseTest
 {
-    public static function setUpBeforeClass()
+    public static function setUpBeforeClass(): void
     {
         if (!\class_exists('GuzzleHttp\\Client')) {
             self::markTestSkipped('guzzlehttp/guzzle package should be installed to run guzzle transport tests');
         }
     }
 
+    protected function setUp(): void
+    {
+        \putenv('http_proxy=');
+    }
+
+    protected function tearDown(): void
+    {
+        parent::tearDown();
+        \putenv('http_proxy=');
+    }
+
     /**
      * @group functional
      */
-    public function testWithEnvironmentalProxy()
+    public function testWithEnvironmentalProxy(): void
     {
         $this->checkProxy($this->_getProxyUrl());
         \putenv('http_proxy='.$this->_getProxyUrl().'/');
@@ -38,7 +52,7 @@ public function testWithEnvironmentalProxy()
     /**
      * @group functional
      */
-    public function testWithEnabledEnvironmentalProxy()
+    public function testWithEnabledEnvironmentalProxy(): void
     {
         $this->checkProxy($this->_getProxyUrl403());
         \putenv('http_proxy='.$this->_getProxyUrl403().'/');
@@ -58,7 +72,7 @@ public function testWithEnabledEnvironmentalProxy()
     /**
      * @group functional
      */
-    public function testWithProxy()
+    public function testWithProxy(): void
     {
         $this->checkProxy($this->_getProxyUrl());
         $client = $this->_getClient(['transport' => 'Guzzle', 'persistent' => false]);
@@ -71,7 +85,7 @@ public function testWithProxy()
     /**
      * @group functional
      */
-    public function testWithoutProxy()
+    public function testWithoutProxy(): void
     {
         $client = $this->_getClient(['transport' => 'Guzzle', 'persistent' => false]);
         $client->getConnection()->setProxy('');
@@ -83,7 +97,7 @@ public function testWithoutProxy()
     /**
      * @group functional
      */
-    public function testBodyReuse()
+    public function testBodyReuse(): void
     {
         $client = $this->_getClient(['transport' => 'Guzzle', 'persistent' => false]);
         $index = $client->getIndex('elastica_body_reuse_test');
@@ -115,7 +129,7 @@ public function testBodyReuse()
     /**
      * @group unit
      */
-    public function testInvalidConnection()
+    public function testInvalidConnection(): void
     {
         $this->expectException(\Elastica\Exception\Connection\GuzzleException::class);
 
@@ -124,20 +138,9 @@ public function testInvalidConnection()
         $client->request('_status', 'GET');
     }
 
-    protected function checkProxy($url)
+    protected function checkProxy($url): void
     {
         $url = \parse_url($url);
         $this->_checkConnection($url['host'], $url['port']);
     }
-
-    protected function setUp()
-    {
-        \putenv('http_proxy=');
-    }
-
-    protected function tearDown()
-    {
-        parent::tearDown();
-        \putenv('http_proxy=');
-    }
 }
diff --git a/tests/Transport/HttpTest.php b/tests/Transport/HttpTest.php
index 8d9e233c21..778f516d9d 100644
--- a/tests/Transport/HttpTest.php
+++ b/tests/Transport/HttpTest.php
@@ -7,12 +7,21 @@
 use Elastica\ResultSet\DefaultBuilder;
 use Elastica\Test\Base as BaseTest;
 
+/**
+ * @internal
+ */
 class HttpTest extends BaseTest
 {
+    protected function tearDown(): void
+    {
+        parent::tearDown();
+        \putenv('http_proxy=');
+    }
+
     /**
      * @group functional
      */
-    public function testCurlNobodyOptionIsResetAfterHeadRequest()
+    public function testCurlNobodyOptionIsResetAfterHeadRequest(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('curl_test');
@@ -40,7 +49,7 @@ public function testCurlNobodyOptionIsResetAfterHeadRequest()
     /**
      * @group functional
      */
-    public function testUnicodeData()
+    public function testUnicodeData(): void
     {
         $client = $this->_getClient();
         $index = $client->getIndex('curl_test');
@@ -73,7 +82,7 @@ public function testUnicodeData()
     /**
      * @group functional
      */
-    public function testWithEnvironmentalProxy()
+    public function testWithEnvironmentalProxy(): void
     {
         $this->checkProxy($this->_getProxyUrl());
         \putenv('http_proxy='.$this->_getProxyUrl().'/');
@@ -92,7 +101,7 @@ public function testWithEnvironmentalProxy()
     /**
      * @group functional
      */
-    public function testWithEnabledEnvironmentalProxy()
+    public function testWithEnabledEnvironmentalProxy(): void
     {
         $this->checkProxy($this->_getProxyUrl403());
         \putenv('http_proxy='.$this->_getProxyUrl403().'/');
@@ -109,7 +118,7 @@ public function testWithEnabledEnvironmentalProxy()
     /**
      * @group functional
      */
-    public function testWithProxy()
+    public function testWithProxy(): void
     {
         $this->checkProxy($this->_getProxyUrl());
         $client = $this->_getClient();
@@ -122,7 +131,7 @@ public function testWithProxy()
     /**
      * @group functional
      */
-    public function testWithoutProxy()
+    public function testWithoutProxy(): void
     {
         $client = $this->_getClient();
         $client->getConnection()->setProxy('');
@@ -134,7 +143,7 @@ public function testWithoutProxy()
     /**
      * @group functional
      */
-    public function testBodyReuse()
+    public function testBodyReuse(): void
     {
         $client = $this->_getClient();
 
@@ -167,7 +176,7 @@ public function testBodyReuse()
     /**
      * @group functional
      */
-    public function testRequestSuccessWithHttpCompressionEnabled()
+    public function testRequestSuccessWithHttpCompressionEnabled(): void
     {
         $client = $this->_getClient(['transport' => ['type' => 'Http', 'compression' => true, 'curl' => [CURLINFO_HEADER_OUT => true]]]);
 
@@ -183,7 +192,7 @@ public function testRequestSuccessWithHttpCompressionEnabled()
     /**
      * @group functional
      */
-    public function testRequestSuccessWithHttpCompressionDisabled()
+    public function testRequestSuccessWithHttpCompressionDisabled(): void
     {
         $client = $this->_getClient(['transport' => ['type' => 'Http', 'compression' => false, 'curl' => [CURLINFO_HEADER_OUT => true]]]);
 
@@ -196,15 +205,9 @@ public function testRequestSuccessWithHttpCompressionDisabled()
         $this->assertArrayHasKey('acknowledged', $createIndexResponse->getData());
     }
 
-    protected function checkProxy($url)
+    protected function checkProxy($url): void
     {
         $url = \parse_url($url);
         $this->_checkConnection($url['host'], $url['port']);
     }
-
-    protected function tearDown()
-    {
-        parent::tearDown();
-        \putenv('http_proxy=');
-    }
 }
diff --git a/tests/Transport/NullTransportTest.php b/tests/Transport/NullTransportTest.php
index cae64bb3b9..95e0c17bcf 100644
--- a/tests/Transport/NullTransportTest.php
+++ b/tests/Transport/NullTransportTest.php
@@ -14,13 +14,15 @@
  *
  * @author James Boehmer <james.boehmer@jamesboehmer.com>
  * @author Jan Domanski <jandom@gmail.com>
+ *
+ * @internal
  */
 class NullTransportTest extends BaseTest
 {
     /** @var NullTransport NullTransport */
     protected $transport;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
         $this->transport = new NullTransport();
@@ -29,7 +31,7 @@ public function setUp()
     /**
      * @group functional
      */
-    public function testEmptyResult()
+    public function testEmptyResult(): void
     {
         // Creates a client with any destination, and verify it returns a response object when executed
         $client = $this->_getClient();
@@ -74,7 +76,7 @@ public function testEmptyResult()
     /**
      * @group functional
      */
-    public function testExec()
+    public function testExec(): void
     {
         $request = new Request('/test');
         $params = ['name' => 'ruflin'];
@@ -90,7 +92,7 @@ public function testExec()
     /**
      * @group unit
      */
-    public function testResponse()
+    public function testResponse(): void
     {
         $resposeString = '';
         $response = new Response($resposeString);
@@ -101,7 +103,7 @@ public function testResponse()
     /**
      * @group unit
      */
-    public function testGenerateDefaultResponse()
+    public function testGenerateDefaultResponse(): void
     {
         $params = ['blah' => 123];
         $response = $this->transport->generateDefaultResponse($params);
diff --git a/tests/Transport/TransportBenchmarkTest.php b/tests/Transport/TransportBenchmarkTest.php
index 2b5dd542af..e2fe5e95ff 100644
--- a/tests/Transport/TransportBenchmarkTest.php
+++ b/tests/Transport/TransportBenchmarkTest.php
@@ -13,6 +13,8 @@
 
 /**
  * @group benchmark
+ *
+ * @internal
  */
 class TransportBenchmarkTest extends BaseTest
 {
@@ -20,24 +22,15 @@ class TransportBenchmarkTest extends BaseTest
     protected $_maxData = 20;
     protected static $_results = [];
 
-    protected function setUp()
-    {
-        parent::setUp();
-        $this->markTestSkipped('Benchmarks currently skipped: it has to be reworked');
-    }
-
-    public static function tearDownAfterClass()
+    public static function tearDownAfterClass(): void
     {
         self::printResults();
     }
 
-    protected function getIndex(array $config): Index
+    protected function setUp(): void
     {
-        $client = $this->_getClient($config);
-        $index = $client->getIndex('benchmark'.self::buildUniqueId());
-        $index->create(['index' => ['number_of_shards' => 1, 'number_of_replicas' => 0]], true);
-
-        return $index;
+        parent::setUp();
+        $this->markTestSkipped('Benchmarks currently skipped: it has to be reworked');
     }
 
     /**
@@ -66,6 +59,8 @@ public function testAddDocument(array $config, string $transport): void
     /**
      * @depends testAddDocument
      * @dataProvider providerTransport
+     *
+     * @param mixed $transport
      */
     public function testRandomRead(array $config, $transport): void
     {
@@ -89,6 +84,8 @@ public function testRandomRead(array $config, $transport): void
     /**
      * @depends testAddDocument
      * @dataProvider providerTransport
+     *
+     * @param mixed $transport
      */
     public function testBulk(array $config, $transport): void
     {
@@ -154,11 +151,11 @@ public function testGetMapping(array $config, string $transport): void
     public function providerTransport(): iterable
     {
         yield [[
-                'transport' => 'Http',
-                'host' => $this->_getHost(),
-                'port' => $this->_getPort(),
-                'persistent' => false,
-            ],
+            'transport' => 'Http',
+            'host' => $this->_getHost(),
+            'port' => $this->_getPort(),
+            'persistent' => false,
+        ],
             'Http:NotPersistent',
         ];
         yield [[
@@ -166,9 +163,18 @@ public function providerTransport(): iterable
             'host' => $this->_getHost(),
             'port' => $this->_getPort(),
             'persistent' => true,
-            ],
+        ],
             'Http:Persistent',
-       ];
+        ];
+    }
+
+    protected function getIndex(array $config): Index
+    {
+        $client = $this->_getClient($config);
+        $index = $client->getIndex('benchmark'.self::buildUniqueId());
+        $index->create(['index' => ['number_of_shards' => 1, 'number_of_replicas' => 0]], true);
+
+        return $index;
     }
 
     protected function getData(string $test): array
diff --git a/tests/UtilTest.php b/tests/UtilTest.php
index 5057d5e399..02f162a1c5 100644
--- a/tests/UtilTest.php
+++ b/tests/UtilTest.php
@@ -7,13 +7,19 @@
 use Elastica\Test\Base as BaseTest;
 use Elastica\Util;
 
+/**
+ * @internal
+ */
 class UtilTest extends BaseTest
 {
     /**
      * @group unit
      * @dataProvider getIsDateMathEscapedPairs
+     *
+     * @param mixed $requestUri
+     * @param mixed $expectedIsEscaped
      */
-    public function testIsDateMathEscaped($requestUri, $expectedIsEscaped)
+    public function testIsDateMathEscaped($requestUri, $expectedIsEscaped): void
     {
         $this->assertEquals($expectedIsEscaped, Util::isDateMathEscaped($requestUri));
     }
@@ -34,8 +40,11 @@ public function getIsDateMathEscapedPairs()
     /**
      * @group unit
      * @dataProvider getEscapeDateMathPairs
+     *
+     * @param mixed $requestUri
+     * @param mixed $expectedEscapedRequestUri
      */
-    public function testEscapeDateMath($requestUri, $expectedEscapedRequestUri)
+    public function testEscapeDateMath($requestUri, $expectedEscapedRequestUri): void
     {
         $this->assertEquals($expectedEscapedRequestUri, Util::escapeDateMath($requestUri));
     }
@@ -65,8 +74,11 @@ public function getEscapeDateMathPairs()
     /**
      * @group unit
      * @dataProvider getEscapeTermPairs
+     *
+     * @param mixed $unescaped
+     * @param mixed $escaped
      */
-    public function testEscapeTerm($unescaped, $escaped)
+    public function testEscapeTerm($unescaped, $escaped): void
     {
         $this->assertEquals($escaped, Util::escapeTerm($unescaped));
     }
@@ -86,8 +98,11 @@ public function getEscapeTermPairs()
     /**
      * @group unit
      * @dataProvider getReplaceBooleanWordsPairs
+     *
+     * @param mixed $before
+     * @param mixed $after
      */
-    public function testReplaceBooleanWords($before, $after)
+    public function testReplaceBooleanWords($before, $after): void
     {
         $this->assertEquals($after, Util::replaceBooleanWords($before));
     }
@@ -107,7 +122,7 @@ public function getReplaceBooleanWordsPairs()
     /**
      * @group unit
      */
-    public function testEscapeTermSpecialCharacters()
+    public function testEscapeTermSpecialCharacters(): void
     {
         $before = '\\+-&&||!(){}[]^"~*?:/<>';
         $after = '\\\\\\+\\-\\&&\\||\\!\\(\\)\\{\\}\\[\\]\\^\\"\\~\\*\\?\\:\\/';
@@ -118,7 +133,7 @@ public function testEscapeTermSpecialCharacters()
     /**
      * @group unit
      */
-    public function testToCamelCase()
+    public function testToCamelCase(): void
     {
         $string = 'hello_world';
         $this->assertEquals('HelloWorld', Util::toCamelCase($string));
@@ -130,7 +145,7 @@ public function testToCamelCase()
     /**
      * @group unit
      */
-    public function testToSnakeCase()
+    public function testToSnakeCase(): void
     {
         $string = 'HelloWorld';
         $this->assertEquals('hello_world', Util::toSnakeCase($string));
@@ -142,7 +157,7 @@ public function testToSnakeCase()
     /**
      * @group unit
      */
-    public function testConvertRequestToCurlCommand()
+    public function testConvertRequestToCurlCommand(): void
     {
         $path = 'test';
         $method = Request::POST;
@@ -164,7 +179,7 @@ public function testConvertRequestToCurlCommand()
     /**
      * @group unit
      */
-    public function testConvertDateTimeObjectWithTimezone()
+    public function testConvertDateTimeObjectWithTimezone(): void
     {
         $dateTimeObject = new \DateTime();
         $timestamp = $dateTimeObject->getTimestamp();
@@ -179,7 +194,7 @@ public function testConvertDateTimeObjectWithTimezone()
     /**
      * @group unit
      */
-    public function testConvertDateTimeObjectWithoutTimezone()
+    public function testConvertDateTimeObjectWithoutTimezone(): void
     {
         $dateTimeObject = new \DateTime();
         $timestamp = $dateTimeObject->getTimestamp();