use get method on config repository to access value

also needed to update the tests to actually use a config repository
rather than just an array, otherwise the tests will fail with a ‘call
to member function get() on array’ message

src/Illuminate/Queue/QueueManager.php

@@ -240,7 +240,7 @@ public function setDefaultDriver($name)
      */
     public function getQueuePrefix()
     {
-        return isset($this->app['config']['queue.prefix']) ? $this->app['config']['queue.prefix'] : null;
+        return $this->app['config']->get('queue.prefix');
     }
 
     /**

tests/Queue/QueueManagerTest.php

@@ -4,6 +4,7 @@
 
 use Mockery as m;
 use PHPUnit\Framework\TestCase;
+use Illuminate\Config\Repository;
 use Illuminate\Queue\QueueManager;
 
 class QueueManagerTest extends TestCase
@@ -15,11 +16,13 @@ public function tearDown()
 
     public function testDefaultConnectionCanBeResolved()
     {
+        $config = new Repository([
+            'queue.default' => 'sync',
+            'queue.connections.sync' => ['driver' => 'sync'],
+        ]);
+
         $app = [
-            'config' => [
-                'queue.default' => 'sync',
-                'queue.connections.sync' => ['driver' => 'sync'],
-            ],
+            'config' => $config,
             'encrypter' => $encrypter = m::mock('Illuminate\Contracts\Encryption\Encrypter'),
         ];
 
@@ -39,11 +42,13 @@ public function testDefaultConnectionCanBeResolved()
 
     public function testOtherConnectionCanBeResolved()
     {
+        $config = new Repository([
+            'queue.default' => 'sync',
+            'queue.connections.foo' => ['driver' => 'bar'],
+        ]);
+
         $app = [
-            'config' => [
-                'queue.default' => 'sync',
-                'queue.connections.foo' => ['driver' => 'bar'],
-            ],
+            'config' => $config,
             'encrypter' => $encrypter = m::mock('Illuminate\Contracts\Encryption\Encrypter'),
         ];
 
@@ -63,10 +68,12 @@ public function testOtherConnectionCanBeResolved()
 
     public function testNullConnectionCanBeResolved()
     {
+        $config = new Repository([
+            'queue.default' => 'null',
+        ]);
+
         $app = [
-            'config' => [
-                'queue.default' => 'null',
-            ],
+            'config' => $config,
             'encrypter' => $encrypter = m::mock('Illuminate\Contracts\Encryption\Encrypter'),
         ];