diff --git a/core/modules/system/tests/modules/serialization_test/lib/Drupal/serialization_test/SerializationTestBundle.php b/core/modules/system/tests/modules/serialization_test/lib/Drupal/serialization_test/SerializationTestBundle.php
new file mode 100644
index 0000000..1acb3f2
--- /dev/null
+++ b/core/modules/system/tests/modules/serialization_test/lib/Drupal/serialization_test/SerializationTestBundle.php
@@ -0,0 +1,26 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\serialization_test\SerializationTestBundle.
+ */
+
+namespace Drupal\serialization_test;
+
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\HttpKernel\Bundle\Bundle;
+use Symfony\Component\Serializer\Serializer;
+
+/**
+ * SerializationTest dependency injection container.
+ */
+class SerializationTestBundle extends Bundle {
+
+  /**
+   * Overrides Symfony\Component\HttpKernel\Bundle\Bundle::build().
+   */
+  public function build(ContainerBuilder $container) {
+    $container->register('serializer.normalizer.serialization_test', 'Drupal\serialization_test\SerializationTestNormalizer')->addTag('normalizer');
+    $container->register('serializer.encoder.serialization_test', 'Drupal\serialization_test\SerializationTestEncoder')->addTag('encoder');
+  }
+}
diff --git a/core/modules/system/tests/modules/serialization_test/lib/Drupal/serialization_test/SerializationTestEncoder.php b/core/modules/system/tests/modules/serialization_test/lib/Drupal/serialization_test/SerializationTestEncoder.php
new file mode 100644
index 0000000..bf1a755
--- /dev/null
+++ b/core/modules/system/tests/modules/serialization_test/lib/Drupal/serialization_test/SerializationTestEncoder.php
@@ -0,0 +1,49 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\serialization_test\SerializationTestEncoder.
+ */
+
+namespace Drupal\serialization_test;
+
+use Symfony\Component\Serializer\Encoder\EncoderInterface;
+
+class SerializationTestEncoder implements EncoderInterface {
+
+  /**
+   * The format that this Encoder supports.
+   *
+   * @var string
+   */
+  static protected $format = 'serialization_test';
+
+  /**
+   * Encodes data into the requested format.
+   *
+   * @param mixed $data
+   *   Data to encode.
+   * @param string $format
+   *   Format name.
+   *
+   * @return string
+   *   A string representation of $data in the requested format.
+   */
+  public function encode($data, $format) {
+    // @see Drupal\serialization_test\SerializationTestNormalizer::normalize().
+    return 'Normalized by ' . $data['normalized_by'] . ', Encoded by SerializationTestEncoder';
+  }
+
+  /**
+   * Checks whether this encoder can encode to the requested format.
+   *
+   * @param string $format
+   *   The short name of the format.
+   *
+   * @return bool
+   *   Returns TRUE if this encoder can encode to the requested format.
+   */
+  public function supportsEncoding($format) {
+    return static::$format === $format;
+  }
+}
diff --git a/core/modules/system/tests/modules/serialization_test/lib/Drupal/serialization_test/SerializationTestNormalizer.php b/core/modules/system/tests/modules/serialization_test/lib/Drupal/serialization_test/SerializationTestNormalizer.php
new file mode 100644
index 0000000..5519fe9
--- /dev/null
+++ b/core/modules/system/tests/modules/serialization_test/lib/Drupal/serialization_test/SerializationTestNormalizer.php
@@ -0,0 +1,55 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\serialization_test\SerializationTestNormalizer.
+ */
+
+namespace Drupal\serialization_test;
+
+use Symfony\Component\Serializer\Normalizer\NormalizerInterface;
+
+class SerializationTestNormalizer implements NormalizerInterface {
+
+  /**
+   * The format that this Normalizer supports.
+   *
+   * @var string
+   */
+  static protected $format = 'serialization_test';
+
+  /**
+   * Normalizes an object into a set of arrays/scalars.
+   *
+   * @param object $object
+   *   Object to normalize.
+   * @param string $format
+   *   Format the normalization result will be encoded as.
+   *
+   * @return array
+   *   An array containing a normalized representation of $object, appropriate
+   *   for encoding to the requested format.
+   */
+  public function normalize($object, $format = NULL) {
+    $normalized = (array) $object;
+    // Add identifying value that can be used to verify that the expected
+    // normalizer was invoked.
+    $normalized['normalized_by'] = 'SerializationTestNormalizer';
+    return $normalized;
+  }
+
+  /**
+   * Checks whether format is supported by this normalizer.
+   *
+   * @param mixed  $data
+   *   Data to normalize.
+   * @param string $format
+   *   Format the normalization result will be encoded as.
+   *
+   * @return bool
+   *   Returns TRUE if the normalizer can handle the request.
+   */
+  public function supportsNormalization($data, $format = NULL) {
+    return static::$format === $format;
+  }
+}
diff --git a/core/modules/system/tests/modules/serialization_test/serialization_test.info b/core/modules/system/tests/modules/serialization_test/serialization_test.info
new file mode 100644
index 0000000..7c6fa97
--- /dev/null
+++ b/core/modules/system/tests/modules/serialization_test/serialization_test.info
@@ -0,0 +1,5 @@
+name = Serialization test module
+description = "Support module for serialization tests."
+package = Testing
+core = 8.x
+hidden = TRUE
diff --git a/core/modules/system/tests/modules/serialization_test/serialization_test.module b/core/modules/system/tests/modules/serialization_test/serialization_test.module
new file mode 100644
index 0000000..c4e35c7
--- /dev/null
+++ b/core/modules/system/tests/modules/serialization_test/serialization_test.module
@@ -0,0 +1,7 @@
+<?php
+
+/**
+ * @file
+ * Helper module for serialization tests. This file is empty, because all
+ * implementation is in autoloaded classes.
+ */
diff --git a/core/modules/system/tests/modules/serilization_test/lib/Drupal/serialization_test/SerializationTestBundle.php b/core/modules/system/tests/modules/serilization_test/lib/Drupal/serialization_test/SerializationTestBundle.php
deleted file mode 100644
index 1acb3f2..0000000
--- a/core/modules/system/tests/modules/serilization_test/lib/Drupal/serialization_test/SerializationTestBundle.php
+++ /dev/null
@@ -1,26 +0,0 @@
-<?php
-
-/**
- * @file
- * Definition of Drupal\serialization_test\SerializationTestBundle.
- */
-
-namespace Drupal\serialization_test;
-
-use Symfony\Component\DependencyInjection\ContainerBuilder;
-use Symfony\Component\HttpKernel\Bundle\Bundle;
-use Symfony\Component\Serializer\Serializer;
-
-/**
- * SerializationTest dependency injection container.
- */
-class SerializationTestBundle extends Bundle {
-
-  /**
-   * Overrides Symfony\Component\HttpKernel\Bundle\Bundle::build().
-   */
-  public function build(ContainerBuilder $container) {
-    $container->register('serializer.normalizer.serialization_test', 'Drupal\serialization_test\SerializationTestNormalizer')->addTag('normalizer');
-    $container->register('serializer.encoder.serialization_test', 'Drupal\serialization_test\SerializationTestEncoder')->addTag('encoder');
-  }
-}
diff --git a/core/modules/system/tests/modules/serilization_test/lib/Drupal/serialization_test/SerializationTestEncoder.php b/core/modules/system/tests/modules/serilization_test/lib/Drupal/serialization_test/SerializationTestEncoder.php
deleted file mode 100644
index bf1a755..0000000
--- a/core/modules/system/tests/modules/serilization_test/lib/Drupal/serialization_test/SerializationTestEncoder.php
+++ /dev/null
@@ -1,49 +0,0 @@
-<?php
-
-/**
- * @file
- * Definition of Drupal\serialization_test\SerializationTestEncoder.
- */
-
-namespace Drupal\serialization_test;
-
-use Symfony\Component\Serializer\Encoder\EncoderInterface;
-
-class SerializationTestEncoder implements EncoderInterface {
-
-  /**
-   * The format that this Encoder supports.
-   *
-   * @var string
-   */
-  static protected $format = 'serialization_test';
-
-  /**
-   * Encodes data into the requested format.
-   *
-   * @param mixed $data
-   *   Data to encode.
-   * @param string $format
-   *   Format name.
-   *
-   * @return string
-   *   A string representation of $data in the requested format.
-   */
-  public function encode($data, $format) {
-    // @see Drupal\serialization_test\SerializationTestNormalizer::normalize().
-    return 'Normalized by ' . $data['normalized_by'] . ', Encoded by SerializationTestEncoder';
-  }
-
-  /**
-   * Checks whether this encoder can encode to the requested format.
-   *
-   * @param string $format
-   *   The short name of the format.
-   *
-   * @return bool
-   *   Returns TRUE if this encoder can encode to the requested format.
-   */
-  public function supportsEncoding($format) {
-    return static::$format === $format;
-  }
-}
diff --git a/core/modules/system/tests/modules/serilization_test/lib/Drupal/serialization_test/SerializationTestNormalizer.php b/core/modules/system/tests/modules/serilization_test/lib/Drupal/serialization_test/SerializationTestNormalizer.php
deleted file mode 100644
index 5519fe9..0000000
--- a/core/modules/system/tests/modules/serilization_test/lib/Drupal/serialization_test/SerializationTestNormalizer.php
+++ /dev/null
@@ -1,55 +0,0 @@
-<?php
-
-/**
- * @file
- * Definition of Drupal\serialization_test\SerializationTestNormalizer.
- */
-
-namespace Drupal\serialization_test;
-
-use Symfony\Component\Serializer\Normalizer\NormalizerInterface;
-
-class SerializationTestNormalizer implements NormalizerInterface {
-
-  /**
-   * The format that this Normalizer supports.
-   *
-   * @var string
-   */
-  static protected $format = 'serialization_test';
-
-  /**
-   * Normalizes an object into a set of arrays/scalars.
-   *
-   * @param object $object
-   *   Object to normalize.
-   * @param string $format
-   *   Format the normalization result will be encoded as.
-   *
-   * @return array
-   *   An array containing a normalized representation of $object, appropriate
-   *   for encoding to the requested format.
-   */
-  public function normalize($object, $format = NULL) {
-    $normalized = (array) $object;
-    // Add identifying value that can be used to verify that the expected
-    // normalizer was invoked.
-    $normalized['normalized_by'] = 'SerializationTestNormalizer';
-    return $normalized;
-  }
-
-  /**
-   * Checks whether format is supported by this normalizer.
-   *
-   * @param mixed  $data
-   *   Data to normalize.
-   * @param string $format
-   *   Format the normalization result will be encoded as.
-   *
-   * @return bool
-   *   Returns TRUE if the normalizer can handle the request.
-   */
-  public function supportsNormalization($data, $format = NULL) {
-    return static::$format === $format;
-  }
-}
diff --git a/core/modules/system/tests/modules/serilization_test/serialization_test.info b/core/modules/system/tests/modules/serilization_test/serialization_test.info
deleted file mode 100644
index 7c6fa97..0000000
--- a/core/modules/system/tests/modules/serilization_test/serialization_test.info
+++ /dev/null
@@ -1,5 +0,0 @@
-name = Serialization test module
-description = "Support module for serialization tests."
-package = Testing
-core = 8.x
-hidden = TRUE
diff --git a/core/modules/system/tests/modules/serilization_test/serialization_test.module b/core/modules/system/tests/modules/serilization_test/serialization_test.module
deleted file mode 100644
index c4e35c7..0000000
--- a/core/modules/system/tests/modules/serilization_test/serialization_test.module
+++ /dev/null
@@ -1,7 +0,0 @@
-<?php
-
-/**
- * @file
- * Helper module for serialization tests. This file is empty, because all
- * implementation is in autoloaded classes.
- */