Merge pull request #455 from ampproject/add/454-invalid-option-value-…

…exception

src/Exception/InvalidOptionValue.php

@@ -0,0 +1,30 @@
+<?php
+
+namespace AmpProject\Exception;
+
+use DomainException;
+
+/**
+ * Exception thrown when an invalid option value was provided.
+ *
+ * @package ampproject/amp-toolbox
+ */
+final class InvalidOptionValue extends DomainException implements AmpException
+{
+    /**
+     * Instantiate an InvalidOptionValue exception for an invalid option value.
+     *
+     * @param string        $option   Name of the option.
+     * @param array<string> $accepted Array of acceptable values.
+     * @param string        $actual   Value that was actually provided.
+     * @return self
+     */
+    public static function forValue($option, $accepted, $actual)
+    {
+        $acceptedString = implode(', ', $accepted);
+        $message = "The value for the option '{$option}' expected the value to be one of "
+                   . "[{$acceptedString}], got '{$actual}' instead.";
+
+        return new self($message);
+    }
+}

tests/Exception/InvalidOptionValueTest.php

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+<?php
+
+namespace AmpProject\Exception;
+
+use AmpProject\Tests\TestCase;
+
+/**
+ * Test the InvalidOptionValue exception.
+ *
+ * @covers \AmpProject\Exception\InvalidOptionValue
+ * @package ampproject/amp-toolbox
+ */
+class InvalidOptionValueTest extends TestCase
+{
+    /**
+     * Test throwing the exception for an invalid option value.
+     */
+    public function testThrowingForSpecName()
+    {
+        $this->expectException(InvalidOptionValue::class);
+        $this->expectExceptionMessage(
+            "The value for the option 'optionName' expected the value to be one of "
+            . "[optionA, optionB], got 'invalid' instead."
+        );
+
+        throw InvalidOptionValue::forValue('optionName', ['optionA', 'optionB'], 'invalid');
+    }
+}