diff --git a/core/modules/system/src/Tests/Common/MergeAttachmentsTest.php b/core/modules/system/src/Tests/Common/MergeAttachmentsTest.php
index f59e395..c09bd42 100644
--- a/core/modules/system/src/Tests/Common/MergeAttachmentsTest.php
+++ b/core/modules/system/src/Tests/Common/MergeAttachmentsTest.php
@@ -8,11 +8,12 @@
 namespace Drupal\system\Tests\Common;
 
 use Drupal\simpletest\KernelTestBase;
+use Drupal\Core\Render\Renderer;
 
 /**
  * Tests the merging of attachments.
  *
- * @see drupal_merge_attached()
+ * @see Renderer::mergeAttachments()
  *
  * @group Common
  */
@@ -40,7 +41,7 @@ function testLibraryMerging() {
         'core/jquery',
       ),
     );
-    $this->assertIdentical($expected['#attached'], drupal_merge_attached($a['#attached'], $b['#attached']), 'Attachments merged correctly.');
+    $this->assertIdentical($expected['#attached'], Renderer::mergeAttachments($a['#attached'], $b['#attached']), 'Attachments merged correctly.');
 
     // Merging in the opposite direction yields the opposite library order.
     $expected['#attached'] = array(
@@ -50,7 +51,7 @@ function testLibraryMerging() {
         'core/drupalSettings',
       ),
     );
-    $this->assertIdentical($expected['#attached'], drupal_merge_attached($b['#attached'], $a['#attached']), 'Attachments merged correctly; opposite merging yields opposite order.');
+    $this->assertIdentical($expected['#attached'], Renderer::mergeAttachments($b['#attached'], $a['#attached']), 'Attachments merged correctly; opposite merging yields opposite order.');
 
     // Merging with duplicates: duplicates are simply retained, it's up to the
     // rest of the system to handle duplicates.
@@ -63,7 +64,7 @@ function testLibraryMerging() {
         'core/drupalSettings',
       ),
     );
-    $this->assertIdentical($expected['#attached'], drupal_merge_attached($a['#attached'], $b['#attached']), 'Attachments merged correctly; duplicates are retained.');
+    $this->assertIdentical($expected['#attached'], Renderer::mergeAttachments($a['#attached'], $b['#attached']), 'Attachments merged correctly; duplicates are retained.');
   }
 
   /**
@@ -98,7 +99,7 @@ function testJsSettingMerging() {
         'bar' => ['a', 'b', 'c'],
       ],
     );
-    $this->assertIdentical($expected['#attached'], drupal_merge_attached($a['#attached'], $b['#attached']), 'Attachments merged correctly.');
+    $this->assertIdentical($expected['#attached'], Renderer::mergeAttachments($a['#attached'], $b['#attached']), 'Attachments merged correctly.');
 
     // Merging in the opposite direction yields the opposite JS setting asset
     // order.
@@ -113,7 +114,7 @@ function testJsSettingMerging() {
         'foo' => ['d'],
       ],
     );
-    $this->assertIdentical($expected['#attached'], drupal_merge_attached($b['#attached'], $a['#attached']), 'Attachments merged correctly; opposite merging yields opposite order.');
+    $this->assertIdentical($expected['#attached'], Renderer::mergeAttachments($b['#attached'], $a['#attached']), 'Attachments merged correctly; opposite merging yields opposite order.');
 
     // Merging with duplicates (simple case).
     $b['#attached']['drupalSettings']['foo'] = ['a', 'b', 'c'];
@@ -128,7 +129,7 @@ function testJsSettingMerging() {
         'bar' => ['a', 'b', 'c'],
       ],
     );
-    $this->assertIdentical($expected['#attached'], drupal_merge_attached($a['#attached'], $b['#attached']));
+    $this->assertIdentical($expected['#attached'], Renderer::mergeAttachments($a['#attached'], $b['#attached']));
 
     // Merging with duplicates (simple case) in the opposite direction yields
     // the opposite JS setting asset order, but also opposite overriding order.
@@ -143,7 +144,7 @@ function testJsSettingMerging() {
         'foo' => ['d', 'b', 'c'],
       ],
     );
-    $this->assertIdentical($expected['#attached'], drupal_merge_attached($b['#attached'], $a['#attached']));
+    $this->assertIdentical($expected['#attached'], Renderer::mergeAttachments($b['#attached'], $a['#attached']));
 
     // Merging with duplicates: complex case.
     // Only the second of these two entries should appear in drupalSettings.
@@ -167,7 +168,7 @@ function testJsSettingMerging() {
     $settings_two_b = array('moduleName' => array('ui' => array('button D', 'button E'), 'magical flag' => 3.14, 'thingiesOnPage' => array('id2' => array())));
     $build['b']['#attached']['drupalSettings']['commonTestRealWorldAlmostIdentical'] = $settings_two_b;
 
-    $merged = drupal_merge_attached($build['a']['#attached'], $build['b']['#attached']);
+    $merged = Renderer::mergeAttachments($build['a']['#attached'], $build['b']['#attached']);
 
     // Test whether #attached can be used to override a previous setting.
     $this->assertIdentical('secondValue', $merged['drupalSettings']['commonTest']);