minor #17632 [FrameworkBundle] Test that ObjectNormalizer is registered (dunglas)

This PR was merged into the 2.7 branch.

Discussion
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[FrameworkBundle] Test that ObjectNormalizer is registered

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

Commits
-------

129b140 [FrameworkBundle] Test that ObjectNormalizer is registered

Author: fabpot

Tests/DependencyInjection/FrameworkExtensionTest.php

@@ -18,6 +18,7 @@
 use Symfony\Component\DependencyInjection\Loader\ClosureLoader;
 use Symfony\Component\DependencyInjection\ParameterBag\ParameterBag;
 use Symfony\Component\DependencyInjection\Reference;
+use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
 use Symfony\Component\Validator\Validation;
 
 abstract class FrameworkExtensionTest extends TestCase
@@ -442,6 +443,17 @@ public function testSerializerEnabled()
         $this->assertTrue($container->has('serializer'));
     }
 
+    public function testObjectNormalizerRegistered()
+    {
+        $container = $this->createContainerFromFile('full');
+
+        $definition = $container->getDefinition('serializer.normalizer.object');
+        $tag = $definition->getTag('serializer.normalizer');
+
+        $this->assertEquals(ObjectNormalizer::class, $definition->getClass());
+        $this->assertEquals(-1000, $tag[0]['priority']);
+    }
+
     public function testAssetHelperWhenAssetsAreEnabled()
     {
         $container = $this->createContainerFromFile('full');