diff --git a/core/modules/locale/src/Tests/LocaleContentTest.php b/core/modules/locale/src/Tests/LocaleContentTest.php
index 3ec3c71..5229eb7 100644
--- a/core/modules/locale/src/Tests/LocaleContentTest.php
+++ b/core/modules/locale/src/Tests/LocaleContentTest.php
@@ -177,26 +177,26 @@ public function testContentTypeDirLang() {
 
     // Check if English node does not have lang tag.
     $this->drupalGet('node/' . $nodes['en']->id());
-    $pattern = '|class="[^"]*node[^"]*"[^<>]*lang="en"|';
-    $this->assertNoPattern($pattern, 'The lang tag has not been assigned to the English node.');
+    $element = $this->xpath('//article[@class and contains(concat(" ", normalize-space(@class), " "), " node ") and @lang="en"]');
+    $this->assertTrue(empty($element), 'The lang tag has not been assigned to the English node.');
 
     // Check if English node does not have dir tag.
-    $pattern = '|class="[^"]*node[^"]*"[^<>]*dir="ltr"|';
-    $this->assertNoPattern($pattern, 'The dir tag has not been assigned to the English node.');
+    $element = $this->xpath('//article[@class and contains(concat(" ", normalize-space(@class), " "), " node ") and @dir="ltr"]');
+    $this->assertTrue(empty($element), 'The dir tag has not been assigned to the English node.');
 
     // Check if Arabic node has lang="ar" & dir="rtl" tags.
     $this->drupalGet('node/' . $nodes['ar']->id());
-    $pattern = '|class="[^"]*node[^"]*"[^<>]*lang="ar" dir="rtl"|';
-    $this->assertPattern($pattern, 'The lang and dir tags have been assigned correctly to the Arabic node.');
+    $element = $this->xpath('//article[@class and contains(concat(" ", normalize-space(@class), " "), " node ") and @lang="ar" and @dir="rtl"]');
+    $this->assertTrue(!empty($element), 'The lang and dir tags have been assigned correctly to the Arabic node.');
 
     // Check if Spanish node has lang="es" tag.
     $this->drupalGet('node/' . $nodes['es']->id());
-    $pattern = '|class="[^"]*node[^"]*"[^<>]*lang="es"|';
-    $this->assertPattern($pattern, 'The lang tag has been assigned correctly to the Spanish node.');
+    $element = $this->xpath('//article[@class and contains(concat(" ", normalize-space(@class), " "), " node ") and @lang="es"]');
+    $this->assertTrue(!empty($element), 'The lang tag has been assigned correctly to the Spanish node.');
 
     // Check if Spanish node does not have dir="ltr" tag.
-    $pattern = '|class="[^"]*node[^"]*"[^<>]*lang="es" dir="ltr"|';
-    $this->assertNoPattern($pattern, 'The dir tag has not been assigned to the Spanish node.');
+    $element = $this->xpath('//article[@class and contains(concat(" ", normalize-space(@class), " "), " node ") and @lang="es" and @dir="ltr"]');
+    $this->assertTrue(empty($element), 'The dir tag has not been assigned to the Spanish node.');
   }
 
 }
diff --git a/core/modules/node/node.module b/core/modules/node/node.module
index d96052d..751663a 100644
--- a/core/modules/node/node.module
+++ b/core/modules/node/node.module
@@ -651,25 +651,6 @@ function template_preprocess_node(&$variables) {
 
   // Add article ARIA role.
   $variables['attributes']['role'] = 'article';
-
-  // Gather node classes.
-  $variables['attributes']['class'][] = 'node';
-  $variables['attributes']['class'][] = drupal_html_class('node--type-' . $node->bundle());
-  if ($node->isPromoted()) {
-    $variables['attributes']['class'][] = 'node--promoted';
-  }
-  if ($node->isSticky()) {
-    $variables['attributes']['class'][] = 'node--sticky';
-  }
-  if (!$node->isPublished()) {
-    $variables['attributes']['class'][] = 'node--unpublished';
-  }
-  if ($variables['view_mode']) {
-    $variables['attributes']['class'][] = drupal_html_class('node--view-mode-' . $variables['view_mode']);
-  }
-  if (isset($node->preview)) {
-    $variables['attributes']['class'][] = 'node--preview';
-  }
 }
 
 /**
diff --git a/core/modules/node/templates/node.html.twig b/core/modules/node/templates/node.html.twig
index a08b064..e29b93e 100644
--- a/core/modules/node/templates/node.html.twig
+++ b/core/modules/node/templates/node.html.twig
@@ -11,10 +11,10 @@
  *   - createdtime: Formatted creation date. Preprocess functions can
  *     reformat it by calling format_date() with the desired parameters on
  *     $variables['node']->getCreatedTime().
- *   - promoted: Whether the node is promoted to the front page.
- *   - sticky: Whether the node is 'sticky'. Sticky nodes are ordered above
+ *   - isPromoted: Whether the node is promoted to the front page.
+ *   - isSticky: Whether the node is 'sticky'. Sticky nodes are ordered above
  *     other non-sticky nodes in teaser listings
- *   - published: Whether the node is published.
+ *   - isPublished: Whether the node is published.
  * - label: The title of the node.
  * - content: All node items. Use {{ content }} to print them all,
  *   or print a subset such as {{ content.field_example }}. Use
@@ -76,7 +76,18 @@
  * @ingroup themeable
  */
 #}
-<article{{ attributes }}>
+{%
+  set classes = [
+    'node',
+    'node--type-' ~ node.bundle|clean_class,
+    node.isPromoted ? 'node--promoted',
+    node.isSticky ? 'node--sticky',
+    not node.isPublished ? 'node--unpublished',
+    'node--view-mode-' ~ view_mode|clean_class,
+    preview ? 'node--preview',
+  ]
+%}
+<article{{ attributes.addClass(classes) }}>
 
   {{ title_prefix }}
   {% if not page %}
@@ -89,15 +100,15 @@
   {% if display_submitted %}
     <footer class="node__meta">
       {{ author_picture }}
-      <div class="node__submitted {{ author_attributes.class }}"{{ author_attributes|without('class') }}>
+      <div{{ author_attributes.addClass('node__submitted') }}>
         {% trans %}Submitted by {{ author_name|passthrough }} on {{ date }}{% endtrans %}
         {{ metadata }}
       </div>
     </footer>
   {% endif %}
 
-  <div class="node__content {{ content_attributes.class }}"{{ content_attributes|without('class') }}>
-    {{ content|without('links') }}
+  <div{{ content_attributes.addClass('node__content') }}>
+      {{ content|without('links') }}
   </div>
 
   {% if content.links %}
diff --git a/core/themes/bartik/templates/node.html.twig b/core/themes/bartik/templates/node.html.twig
index d45b0f0..9e95734 100644
--- a/core/themes/bartik/templates/node.html.twig
+++ b/core/themes/bartik/templates/node.html.twig
@@ -11,10 +11,10 @@
  *   - createdtime: Formatted creation date. Preprocess functions can
  *     reformat it by calling format_date() with the desired parameters on
  *     $variables['node']->getCreatedTime().
- *   - promoted: Whether the node is promoted to the front page.
- *   - sticky: Whether the node is 'sticky'. Sticky nodes are ordered above
+ *   - isPromoted: Whether the node is promoted to the front page.
+ *   - isSticky: Whether the node is 'sticky'. Sticky nodes are ordered above
  *     other non-sticky nodes in teaser listings
- *   - published: Whether the node is published.
+ *   - isPublished: Whether the node is published.
  * - label: The title of the node.
  * - content: All node items. Use {{ content }} to print them all,
  *   or print a subset such as {{ content.field_example }}. Use
@@ -71,12 +71,24 @@
  * @see template_preprocess_node()
  */
 #}
-<article class="{{ attributes.class }} clearfix"{{ attributes|without('class') }}>
+{%
+  set classes = [
+    'node',
+    'node--type-' ~ node.bundle|clean_class,
+    node.isPromoted ? 'node--promoted',
+    node.isSticky ? 'node--sticky',
+    not node.isPublished ? 'node--unpublished',
+    'node--view-mode-' ~ view_mode|clean_class,
+    preview ? 'node--preview',
+    'clearfix',
+  ]
+%}
+<article{{ attributes.addClass(classes) }}>
 
   <header>
     {{ title_prefix }}
     {% if not page %}
-      <h2 class="node__title {{ title_attributes.class }}"{{ title_attributes|without('class') }}>
+      <h2{{ title_attributes.addClass('node__title') }}>
         <a href="{{ url }}" rel="bookmark">{{ label }}</a>
       </h2>
     {% endif %}
@@ -93,7 +105,7 @@
     {% endif %}
   </header>
 
-  <div class="node__content clearfix {{ content_attributes.class }}"{{ content_attributes|without('class') }}>
+  <div{{ content_attributes.addClass('node__content clearfix') }}>
     {{ content|without('comment', 'links') }}
   </div>