[#1085] Replace usage of ClassName::class with strings for < PHP 5.5 compatibility

Author: mickadoo

Tests/Serializer/CallbackTest.php

@@ -1,21 +1,20 @@
 <?php
 
 use \FOS\ElasticaBundle\Serializer\Callback;
-use \Symfony\Component\Serializer\Serializer;
 
 class CallbackTest extends PHPUnit_Framework_TestCase
 {
     public function testSerializerMustHaveSerializeMethod()
     {
         $callback = new Callback();
-        $this->setExpectedException(RuntimeException::class, 'The serializer must have a "serialize" method.');
+        $this->setExpectedException('RuntimeException', 'The serializer must have a "serialize" method.');
         $callback->setSerializer(new \stdClass());
     }
 
     public function testSetGroupsWorksWithValidSerializer()
     {
         $callback = new Callback();
-        $serializer = $this->getMock(Serializer::class, [], [], '', false);
+        $serializer = $this->getMock('Symfony\Component\Serializer\Serializer', [], [], '', false);
         $callback->setSerializer($serializer);
 
         $callback->setGroups(array('foo'));
@@ -28,7 +27,7 @@ public function testSetGroupsFailsWithInvalidSerializer()
         $callback->setSerializer($serializer);
 
         $this->setExpectedException(
-            RuntimeException::class,
+            'RuntimeException',
             'Setting serialization groups requires using "JMS\Serializer\Serializer" or '
                 . '"Symfony\Component\Serializer\Serializer"'
         );