diff --git a/core/modules/serialization/src/Tests/CollectionTest.php b/core/modules/serialization/src/Tests/CollectionTest.php
deleted file mode 100644
index cedaddb..0000000
--- a/core/modules/serialization/src/Tests/CollectionTest.php
+++ /dev/null
@@ -1,113 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\serialization\Tests\CollectionTest.
- */
-
-namespace Drupal\serialization\Tests;
-
-use Drupal\serialization\Collection;
-use Drupal\Tests\UnitTestCase;
-
-/**
- * Tests the Collection class.
- *
- * @group Serialization
- *
- * @coversDefaultClass \Drupal\serialization\Collection
- */
-class CollectionTest extends UnitTestCase {
-  /**
-   * {@inheritdoc}
-   */
-  public static function getInfo() {
-    return array(
-      'name' => 'CollectionTest',
-      'description' => 'Tests the Collection class used for serializing collections.',
-      'group' => 'Serialization',
-    );
-  }
-
-  /**
-   * Tests the constructor, as well as getters and setters.
-   *
-   * @covers ::__construct
-   * @covers ::getTitle
-   * @covers ::setTitle
-   * @covers ::getURI
-   * @covers ::setURI
-   * @covers ::getDescription
-   * @covers ::setDescription
-   */
-  public function testConstructor() {
-    $collection_id = $this->randomMachineName();
-    $collection = new Collection($collection_id);
-    $this->assertSame($collection_id, $collection->getCollectionId(), 'Id has been set accordingly');
-
-    $this->assertEquals(NULL, $collection->getTitle(), 'Collection title is not set');
-    $collection->setTitle($collection_id);
-    $this->assertEquals($collection_id, $collection->getTitle(), 'Collection title has been set');
-
-    $this->assertEquals(NULL, $collection->getUri(), 'Collection URI is not set');
-    $collection->setURI("http://example.com/$collection_id");
-    $this->assertEquals("http://example.com/$collection_id", $collection->getUri(), 'Collection URI has been set');
-
-    $this->assertEquals(NULL, $collection->getDescription(), 'Collection description is not set');
-    $collection->setDescription($collection_id);
-    $this->assertEquals($collection_id, $collection->getDescription(), 'Collection description has been set');
-  }
-
-  /**
-   * Tests items setter and getter as well as iteration.
-   *
-   * @covers ::setItems
-   * @covers ::getItems
-   * @covers ::getIterator
-   */
-  public function testSettingItemsAndIterating() {
-    $collection = new Collection('example');
-
-    $this->assertEquals($collection->getItems(), NULL, 'By default the  items are NULL');
-
-    $example = array(1, 2, 3);
-    $collection->setItems($example);
-    $this->assertEquals($collection->getItems(), $example, 'Setters and getters work on the Collection');
-
-    // Iterating over collection returns the same array.
-    $array = array();
-    foreach ($collection as $k => $v) {
-      $array[$k] = $v;
-    }
-    $this->assertEquals($array, $collection->getItems(), 'Array filled via iteration matches the array of the getter');
-  }
-
-  /**
-   * Tests setters and getters for link relations.
-   *
-   * @covers ::setLinks
-   * @covers ::getLinks
-   * @covers ::hasLinks
-   * @covers ::getLink
-   * @covers ::setLink
-   */
-  public function testSetGetHasLinks() {
-    $collection = new Collection('example');
-    $this->assertFalse($collection->hasLinks(), 'By default a Collection does not have any link relations');
-
-    $collection->setURI('http://example.com/collection');
-    $this->assertFalse($collection->hasLinks(), 'Setting the main URI (self) of the collection does not count as a link relation');
-
-    $this->assertEquals($collection->getLink('next'), NULL, 'Before setting a link for a type the getter returns NULL');
-    $collection->setLink('next', 'http://example.com/collection/?page=1');
-    $this->assertEquals($collection->getLink('next'), 'http://example.com/collection/?page=1', 'After setting a link for a type the getter returns correctly');
-    $this->assertTrue($collection->hasLinks(), 'Setting another URI (self) of the collection does not count as a link relation');
-    $this->assertEquals($collection->getLinks(), array('next' => 'http://example.com/collection/?page=1'));
-
-    $collection->setLinks(array());
-    $this->assertFalse($collection->hasLinks(), 'After resetting links to an empty array, hasLinks should return false');
-
-    $collection->setLinks(NULL);
-    $this->assertFalse($collection->hasLinks(), 'After resetting links to NULL, hasLinks should return false');
-  }
-}
diff --git a/core/modules/serialization/tests/Drupal/serialization/Tests/CollectionTest.php b/core/modules/serialization/tests/src/Unit/CollectionTest.php
similarity index 94%
rename from core/modules/serialization/tests/Drupal/serialization/Tests/CollectionTest.php
rename to core/modules/serialization/tests/src/Unit/CollectionTest.php
index 7d8f0aa..52ccd5b 100644
--- a/core/modules/serialization/tests/Drupal/serialization/Tests/CollectionTest.php
+++ b/core/modules/serialization/tests/src/Unit/CollectionTest.php
@@ -5,7 +5,7 @@
  * Contains \Drupal\serialization\Tests\CollectionTest.
  */
 
-namespace Drupal\serialization\Tests;
+namespace Drupal\Tests\serialization\Unit;
 
 use Drupal\serialization\Collection;
 use Drupal\Tests\UnitTestCase;
@@ -41,7 +41,7 @@ public static function getInfo() {
    * @covers ::setDescription
    */
   public function testConstructor() {
-    $collection_id = $this->randomName();
+    $collection_id = $this->randomMachineName();
     $collection = new Collection($collection_id);
     $this->assertSame($collection_id, $collection->getCollectionId(), 'Id has been set accordingly');
 
@@ -106,8 +106,5 @@ public function testSetGetHasLinks() {
 
     $collection->setLinks(array());
     $this->assertFalse($collection->hasLinks(), 'After resetting links to an empty array, hasLinks should return false');
-
-    $collection->setLinks(NULL);
-    $this->assertFalse($collection->hasLinks(), 'After resetting links to NULL, hasLinks should return false');
   }
 }