diff --git a/core/tests/Drupal/Tests/Core/Render/BubbleableMetadataTest.php b/core/tests/Drupal/Tests/Core/Render/BubbleableMetadataTest.php
index c5942a8..51ff506 100644
--- a/core/tests/Drupal/Tests/Core/Render/BubbleableMetadataTest.php
+++ b/core/tests/Drupal/Tests/Core/Render/BubbleableMetadataTest.php
@@ -359,241 +359,258 @@ function testMergeAttachmentsLibraryMerging() {
    * Tests feed asset merging.
    *
    * @covers ::mergeAttachments
+   *
+   * @dataProvider providerTestMergeAttachmentsFeedMerging
    */
-  function testMergeAttachmentsFeedMerging() {
-    $a['#attached'] = array(
-      'feed' => array(
-        array(
-          'aggregator/rss',
-          'Feed title',
-        ),
-      ),
-    );
-    $b['#attached'] = array(
-      'feed' => array(
-        array(
-          'taxonomy/term/1/feed',
-          'RSS - foo',
-        ),
-      ),
-    );
-    $expected['#attached'] = array(
-      'feed' => array(
-        array(
-          'aggregator/rss',
-          'Feed title',
-        ),
-        array(
-          'taxonomy/term/1/feed',
-          'RSS - foo',
-        ),
-      ),
-    );
-    $this->assertSame($expected['#attached'], BubbleableMetadata::mergeAttachments($a['#attached'], $b['#attached']), 'Attachments merged correctly.');
+  function testMergeAttachmentsFeedMerging($a, $b, $expected) {
+    $this->assertSame($expected, BubbleableMetadata::mergeAttachments($a, $b));
+  }
+
+  /**
+   * Data provider for testMergeAttachmentsFeedMerging
+   *
+   * @return array
+   */
+  public function providerTestMergeAttachmentsFeedMerging() {
+    $feed_a =         [
+      'aggregator/rss',
+      'Feed title',
+    ];
+
+    $feed_b =         [
+      'taxonomy/term/1/feed',
+      'RSS - foo',
+    ];
+
+    $a = [
+      'feed' => [
+        $feed_a,
+      ],
+    ];
+    $b = [
+      'feed' => [
+        $feed_b,
+      ],
+    ];
+
+    $expected_a = [
+      'feed' => [
+        $feed_a,
+        $feed_b,
+      ],
+    ];
 
     // Merging in the opposite direction yields the opposite library order.
-    $expected['#attached'] = array(
-      'feed' => array(
-        array(
-          'taxonomy/term/1/feed',
-          'RSS - foo',
-        ),
-        array(
-          'aggregator/rss',
-          'Feed title',
-        ),
-      ),
-    );
-    $this->assertSame($expected['#attached'], BubbleableMetadata::mergeAttachments($b['#attached'], $a['#attached']), 'Attachments merged correctly; opposite merging yields opposite order.');
+    $expected_b = [
+      'feed' => [
+        $feed_b,
+        $feed_a,
+      ],
+    ];
+
+    return [
+      [$a, $b, $expected_a],
+      [$b, $a, $expected_b],
+    ];
   }
 
   /**
    * Tests html_head asset merging.
    *
    * @covers ::mergeAttachments
+   *
+   * @dataProvider providerTestMergeAttachmentsHtmlHeadMerging
    */
-  function testMergeAttachmentsHtmlHeadMerging() {
-    $a['#attached'] = array(
-      'html_head' => array(
-        array(
-          '#tag' => 'meta',
-          '#attributes' => array(
-            'charset' => 'utf-8',
-          ),
-          '#weight' => -1000,
-        ),
+  function testMergeAttachmentsHtmlHeadMerging($a, $b, $expected) {
+    $this->assertSame($expected, BubbleableMetadata::mergeAttachments($a, $b));
+  }
+
+  /**
+   * Data provider for testMergeAttachmentsHtmlHeadMerging
+   *
+   * @return array
+   */
+  public function providerTestMergeAttachmentsHtmlHeadMerging() {
+    $meta = [
+      '#tag' => 'meta',
+      '#attributes' => [
+        'charset' => 'utf-8',
+      ],
+      '#weight' => -1000,
+    ];
+
+    $html_tag = [
+      '#type' => 'html_tag',
+      '#tag' => 'meta',
+      '#attributes' => [
+        'name' => 'Generator',
+        'content' => 'Kitten 1.0 (https://www.drupal.org/project/kitten)',
+      ],
+    ];
+
+    $a = [
+      'html_head' => [
+        $meta,
         'system_meta_content_type',
-      ),
-    );
-    $b['#attached'] = array(
-      'html_head' => array(
-        array(
-          '#type' => 'html_tag',
-          '#tag' => 'meta',
-          '#attributes' => array(
-            'name' => 'Generator',
-            'content' => 'Kitten 1.0 (https://www.drupal.org/project/kitten)',
-          ),
-        ),
+      ],
+    ];
+
+    $b = [
+      'html_head' => [
+        $html_tag,
         'system_meta_generator',
-      ),
-    );
-    $expected['#attached'] = array(
-      'html_head' => array(
-        array(
-          '#tag' => 'meta',
-          '#attributes' => array(
-            'charset' => 'utf-8',
-          ),
-          '#weight' => -1000,
-        ),
+      ],
+    ];
+
+    $expected_a = [
+      'html_head' => [
+        $meta,
         'system_meta_content_type',
-        array(
-          '#type' => 'html_tag',
-          '#tag' => 'meta',
-          '#attributes' => array(
-            'name' => 'Generator',
-            'content' => 'Kitten 1.0 (https://www.drupal.org/project/kitten)',
-          ),
-        ),
+        $html_tag,
         'system_meta_generator',
-      ),
-    );
-    $this->assertSame($expected['#attached'], BubbleableMetadata::mergeAttachments($a['#attached'], $b['#attached']), 'Attachments merged correctly.');
+      ],
+    ];
 
     // Merging in the opposite direction yields the opposite library order.
-    $expected['#attached'] = array(
-      'html_head' => array(
-        array(
-          '#type' => 'html_tag',
-          '#tag' => 'meta',
-          '#attributes' => array(
-            'name' => 'Generator',
-            'content' => 'Kitten 1.0 (https://www.drupal.org/project/kitten)',
-          ),
-        ),
+    $expected_b = [
+      'html_head' => [
+        $html_tag,
         'system_meta_generator',
-        array(
-          '#tag' => 'meta',
-          '#attributes' => array(
-            'charset' => 'utf-8',
-          ),
-          '#weight' => -1000,
-        ),
+        $meta,
         'system_meta_content_type',
-      ),
-    );
-    $this->assertSame($expected['#attached'], BubbleableMetadata::mergeAttachments($b['#attached'], $a['#attached']), 'Attachments merged correctly; opposite merging yields opposite order.');
+      ],
+    ];
+
+    return [
+      [$a, $b, $expected_a],
+      [$b, $a, $expected_b],
+    ];
   }
 
   /**
    * Tests html_head_link asset merging.
    *
    * @covers ::mergeAttachments
+   *
+   * @dataProvider providerTestMergeAttachementsHtmlHeadLinkMerging
    */
-  function testMergeAttachementsHtmlHeadLinkMerging() {
-    $a['#attached'] = array(
-      'html_head_link' => array(
-        array(
-          'rel' => 'rel',
-          'href' => 'http://rel.example.com',
-        ),
+  function testMergeAttachementsHtmlHeadLinkMerging($a, $b, $expected) {
+    $this->assertSame($expected, BubbleableMetadata::mergeAttachments($a, $b));
+  }
+
+  /**
+   * Data provider for testMergeAttachementsHtmlHeadLinkMerging
+   *
+   * @return array
+   */
+  public function providerTestMergeAttachementsHtmlHeadLinkMerging() {
+    $rel =         [
+      'rel' => 'rel',
+      'href' => 'http://rel.example.com',
+    ];
+
+    $shortlink =         [
+      'rel' => 'shortlink',
+      'href' => 'http://shortlink.example.com',
+    ];
+
+    $a = [
+      'html_head_link' => [
+        $rel,
         TRUE,
-      ),
-    );
-    $b['#attached'] = array(
-      'html_head_link' => array(
-        array(
-          'rel' => 'shortlink',
-          'href' => 'http://shortlink.example.com',
-        ),
+      ],
+    ];
+
+    $b = [
+      'html_head_link' => [
+        $shortlink,
         FALSE,
-      ),
-    );
-    $expected['#attached'] = array(
-      'html_head_link' => array(
-        array(
-          'rel' => 'rel',
-          'href' => 'http://rel.example.com',
-        ),
+      ],
+    ];
+
+    $expected_a = [
+      'html_head_link' => [
+        $rel,
         TRUE,
-        array(
-          'rel' => 'shortlink',
-          'href' => 'http://shortlink.example.com',
-        ),
+        $shortlink,
         FALSE,
-      ),
-    );
-    $this->assertSame($expected['#attached'], BubbleableMetadata::mergeAttachments($a['#attached'], $b['#attached']), 'Attachments merged correctly.');
+      ],
+    ];
 
     // Merging in the opposite direction yields the opposite library order.
-    $expected['#attached'] = array(
-      'html_head_link' => array(
-        array(
-          'rel' => 'shortlink',
-          'href' => 'http://shortlink.example.com',
-        ),
+    $expected_b = [
+      'html_head_link' => [
+        $shortlink,
         FALSE,
-        array(
-          'rel' => 'rel',
-          'href' => 'http://rel.example.com',
-        ),
+        $rel,
         TRUE,
-      ),
-    );
-    $this->assertSame($expected['#attached'], BubbleableMetadata::mergeAttachments($b['#attached'], $a['#attached']), 'Attachments merged correctly; opposite merging yields opposite order.');
+      ],
+    ];
+
+    return [
+      [$a, $b, $expected_a],
+      [$b, $a, $expected_b],
+    ];
   }
 
   /**
    * Tests http_header asset merging.
    *
    * @covers ::mergeAttachments
+   *
+   * @dataProvider providerTestMergeAttachmentsHttpHeaderMerging
    */
-  function testMergeAttachmentsHttpHeaderMerging() {
-    $a['#attached'] = array(
-      'http_header' => array(
-        array(
-          'Content-Type',
-          'application/rss+xml; charset=utf-8',
-        ),
-      ),
-    );
-    $b['#attached'] = array(
-      'http_header' => array(
-        array(
-          'Expires',
-          'Sun, 19 Nov 1978 05:00:00 GMT',
-        ),
-      ),
-    );
-    $expected['#attached'] = array(
-      'http_header' => array(
-        array(
-          'Content-Type',
-          'application/rss+xml; charset=utf-8',
-        ),
-        array(
-          'Expires',
-          'Sun, 19 Nov 1978 05:00:00 GMT',
-        ),
-      ),
-    );
-    $this->assertSame($expected['#attached'], BubbleableMetadata::mergeAttachments($a['#attached'], $b['#attached']), 'Attachments merged correctly.');
+  function testMergeAttachmentsHttpHeaderMerging($a, $b, $expected) {
+    $this->assertSame($expected, BubbleableMetadata::mergeAttachments($a, $b));
+  }
+
+  /**
+   * Data provider for testMergeAttachmentsHttpHeaderMerging
+   *
+   * @return array
+   */
+  public function providerTestMergeAttachmentsHttpHeaderMerging() {
+    $content_type = [
+      'Content-Type',
+      'application/rss+xml; charset=utf-8',
+    ];
+
+    $expires = [
+      'Expires',
+      'Sun, 19 Nov 1978 05:00:00 GMT',
+    ];
+
+    $a = [
+      'http_header' => [
+        $content_type,
+      ],
+    ];
+
+    $b = [
+      'http_header' => [
+        $expires,
+      ],
+    ];
+
+    $expected_a = [
+      'http_header' => [
+        $content_type,
+        $expires,
+      ],
+    ];
 
     // Merging in the opposite direction yields the opposite library order.
-    $expected['#attached'] = array(
-      'http_header' => array(
-        array(
-          'Expires',
-          'Sun, 19 Nov 1978 05:00:00 GMT',
-        ),
-        array(
-          'Content-Type',
-          'application/rss+xml; charset=utf-8',
-        ),
-      ),
-    );
-    $this->assertSame($expected['#attached'], BubbleableMetadata::mergeAttachments($b['#attached'], $a['#attached']), 'Attachments merged correctly; opposite merging yields opposite order.');
+    $expected_b = [
+      'http_header' => [
+        $expires,
+        $content_type,
+      ],
+    ];
+
+    return [
+      [$a, $b, $expected_a],
+      [$b, $a, $expected_b],
+    ];
   }
 
 }