[Form] add test to avoid regression of #14891

src/Symfony/Component/Form/Tests/Extension/Validator/ValidatorExtensionTest.php

@@ -17,7 +17,9 @@ class ValidatorExtensionTest extends \PHPUnit_Framework_TestCase
 {
     public function test2Dot5ValidationApi()
     {
-        $validator = $this->getMock('Symfony\Component\Validator\Validator\ValidatorInterface');
+        $validator = $this->getMockBuilder('Symfony\Component\Validator\Validator\RecursiveValidator')
+            ->disableOriginalConstructor()
+            ->getMock();
         $metadata = $this->getMockBuilder('Symfony\Component\Validator\Mapping\ClassMetadata')
             ->disableOriginalConstructor()
             ->getMock();
@@ -36,6 +38,10 @@ class ValidatorExtensionTest extends \PHPUnit_Framework_TestCase
             ->method('addPropertyConstraint')
             ->with('children', $this->isInstanceOf('Symfony\Component\Validator\Constraints\Valid'));
 
+        $validator
+            ->expects($this->never())
+            ->method('getMetadataFactory');
+
         $extension = new ValidatorExtension($validator);
         $guesser = $extension->loadTypeGuesser();