diff --git a/core/modules/system/lib/Drupal/system/Tests/Serialization/EntitySerializationTest.php b/core/modules/system/lib/Drupal/system/Tests/Serialization/EntitySerializationTest.php
index 89fa5ce..089d52a 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Serialization/EntitySerializationTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Serialization/EntitySerializationTest.php
@@ -12,6 +12,7 @@
 use Drupal\Core\Serialization\JsonEncoder;
 use Drupal\Core\Serialization\ComplexDataNormalizer;
 use Drupal\Core\Serialization\TypedDataNormalizer;
+use Symfony\Component\Yaml\Dumper;
 
 /**
  * Tests entity normalization and serialization of supported core formats.
@@ -153,5 +154,14 @@ public function testSerialize() {
     $this->assertIdentical($actual, $expected);
     $actual = $serializer->serialize($normalized, 'xml');
     $this->assertIdentical($actual, $expected);
+
+    // Test YAML serialization.
+    $dumper = new Dumper();
+    $dumper->setIndentation(2);
+    $expected = $dumper->dump($normalized, PHP_INT_MAX);
+    $actual = $serializer->serialize($this->entity, 'yaml');
+    $this->assertIdentical($actual, $expected);
+    $actual = $serializer->serialize($normalized, 'yaml');
+    $this->assertIdentical($actual, $expected);
   }
 }