diff --git a/core/modules/system/lib/Drupal/system/Tests/Common/RenderElementTypesTest.php b/core/modules/system/lib/Drupal/system/Tests/Common/RenderElementTypesTest.php
index 001b807..ef76a07 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Common/RenderElementTypesTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Common/RenderElementTypesTest.php
@@ -8,10 +8,6 @@
 namespace Drupal\system\Tests\Common;
 
 use Drupal\Component\Utility\String;
-use Drupal\Component\Utility\UrlHelper;
-use Drupal\Component\Utility\Xss;
-use Drupal\Core\Language\Language;
-use Drupal\Core\Template\Attribute;
 use Drupal\simpletest\DrupalUnitTestBase;
 
 /**
@@ -44,216 +40,72 @@ protected function setUp() {
    * Asserts that an array of elements is rendered properly.
    *
    * @param array $elements
-   *   An array of associative arrays describing render elements and their
-   *   expected markup. Each item in $elements must contain the following:
-   *   - 'name': This human readable description will be displayed on the test
-   *     results page.
-   *   - 'value': This is the render element to test.
-   *   - 'expected': This is the expected markup for the element in 'value'.
+   *   The render element array to test.
+   * @param string $expected_html
+   *   The expected markup.
+   * @param string $message
+   *   Assertion message.
    */
-  function assertElements($elements) {
-    foreach($elements as $element) {
-      // More complicated "expected" strings may contain placeholders.
-      if (!empty($element['placeholders'])) {
-        $element['expected'] = String::format($element['expected'], $element['placeholders']);
-      }
+  protected function assertElements(array $elements, $expected_html, $message) {
+    $actual_html = drupal_render($elements);
 
-      // We don't care about whitespace for the sake of comparing markup.
-      $value = new \DOMDocument();
-      $value->preserveWhiteSpace = FALSE;
-      $value->loadXML(drupal_render($element['value']));
+    $out = '<table><tr>';
+    $out .= '<td valign="top"><pre>' . String::checkPlain($expected_html) . '</pre></td>';
+    $out .= '<td valign="top"><pre>' . String::checkPlain($actual_html) . '</pre></td>';
+    $out .= '</tr></table>';
+    $this->verbose($out);
 
-      $expected = new \DOMDocument();
-      $expected->preserveWhiteSpace = FALSE;
-      $expected->loadXML($element['expected']);
-
-      $message = isset($element['name']) ? '"' . $element['name'] . '" input rendered correctly by drupal_render().' : NULL;
-      $this->assertIdentical($value->saveXML(), $expected->saveXML(), $message);
-    }
+    $this->assertIdentical($actual_html, $expected_html, String::checkPlain($message));
   }
 
   /**
    * Tests system #type 'container'.
    */
   function testContainer() {
-    $elements = array(
-      // Basic container with no attributes.
-      array(
-        'name' => "#type 'container' with no HTML attributes",
-        'value' => array(
-          '#type' => 'container',
-          '#markup' => 'foo',
-        ),
-        'expected' => '<div>foo</div>' . "\n",
-      ),
-      // Container with a class.
-      array(
-        'name' => "#type 'container' with a class HTML attribute",
-        'value' => array(
-          '#type' => 'container',
-          '#markup' => 'foo',
-          '#attributes' => array(
-            'class' => 'bar',
-          ),
-        ),
-        'expected' => '<div class="bar">foo</div>' . "\n",
+    // Basic container with no attributes.
+    $this->assertElements(array(
+      '#type' => 'container',
+      '#markup' => 'foo',
+    ), "<div>foo</div>\n", "#type 'container' with no HTML attributes");
+
+    // Container with a class.
+    $this->assertElements(array(
+      '#type' => 'container',
+      '#markup' => 'foo',
+      '#attributes' => array(
+        'class' => 'bar',
       ),
-      // Container with children.
-      array(
-        'name' => "#type 'container' with child elements",
-        'value' => array(
-          '#type' => 'container',
-          'child' => array(
-            '#markup' => 'foo',
-          ),
-        ),
-        'expected' => '<div>foo</div>' . "\n",
-      ),
-    );
+    ), '<div class="bar">foo</div>' . "\n", "#type 'container' with a class HTML attribute");
 
-    $this->assertElements($elements);
+    // Container with children.
+    $this->assertElements(array(
+      '#type' => 'container',
+      'child' => array(
+        '#markup' => 'foo',
+      ),
+    ), "<div>foo</div>\n", "#type 'container' with child elements");
   }
 
   /**
    * Tests system #type 'html_tag'.
    */
   function testHtmlTag() {
-    $elements = array(
-      // Test auto-closure meta tag generation.
-      array(
-        'name' => "#type 'html_tag' auto-closure meta tag generation",
-        'value' => array(
-          '#type' => 'html_tag',
-          '#tag' => 'meta',
-          '#attributes' => array(
-            'name' => 'description',
-            'content' => 'Drupal test',
-          ),
-        ),
-        'expected' => '<meta name="description" content="Drupal test" />' . "\n",
-      ),
-      // Test title tag generation.
-      array(
-        'name' => "#type 'html_tag' title tag generation",
-        'value' => array(
-          '#type' => 'html_tag',
-          '#tag' => 'title',
-          '#value' => 'title test',
-        ),
-        'expected' => '<title>title test</title>' . "\n",
-      ),
-    );
-
-    $this->assertElements($elements);
-  }
-
-  /**
-   * Tests common #theme 'maintenance_page'.
-   */
-  function testMaintenancePage() {
-    // We need to simulate a lot of what would happen in the preprocess, or
-    // there's no way to make these tests portable.
-
-    // HTML element attributes.
-    $html_attributes = new Attribute;
-    $language_interface = \Drupal::service('language_manager')->getCurrentLanguage();
-    $html_attributes['lang'] = $language_interface->id;
-    $html_attributes['dir'] = $language_interface->direction ? 'rtl' : 'ltr';
-
-    $site_config = \Drupal::config('system.site');
-
-    // Add favicon.
-    $favicon = theme_get_setting('favicon.url');
-    $type = theme_get_setting('favicon.mimetype');
-    drupal_add_html_head_link(array('rel' => 'shortcut icon', 'href' => UrlHelper::stripDangerousProtocols($favicon), 'type' => $type));
-
-    // Build CSS links.
-    drupal_static_reset('_drupal_add_css');
-    $default_css = array(
-      '#attached' => array(
-        'library' => array(
-          'core/normalize',
-          'system/maintenance',
-        ),
+    // Test auto-closure meta tag generation.
+    $this->assertElements(array(
+      '#type' => 'html_tag',
+      '#tag' => 'meta',
+      '#attributes' => array(
+        'name' => 'description',
+        'content' => 'Drupal test',
       ),
-    );
-    drupal_render($default_css);
-    $css = _drupal_add_css();
-
-    // Simulate the expected output of a "vanilla" maintenance page.
-    $expected = <<<EOT
-<!DOCTYPE html>
-<html!html_attributes>
-  <head>
-    !head
-    <title>!head_title</title>
-    !styles
-    !scripts
-  </head>
-  <body class="!attributes.class">
-    <div class="l-container">
-      <header role="banner">
-        <a href="!front_page" title="Home" rel="home">
-          <img src="!logo" alt="Home"/>
-        </a>
-        <div class="name-and-slogan">
-          <h1 class="site-name">
-            <a href="!front_page" title="Home" rel="home">!site_name</a>
-          </h1>
-        </div>
-      </header>
-      <main role="main">
-        !title
-        !content
-      </main>
-    </div>
-  </body>
-</html>
-EOT;
-
-    $placeholders = array(
-      '!html_attributes' => $html_attributes->__toString(),
-      '!head' => drupal_get_html_head(),
-      '!head_title' => $site_config->get('name'),
-      '!styles' => drupal_get_css($css),
-      '!scripts' => drupal_get_js(),
-      '!attributes.class' => 'maintenance-page in-maintenance no-sidebars',
-      '!front_page' => url(),
-      '!logo' => theme_get_setting('logo.url'),
-      '!site_name' => $site_config->get('name'),
-      '!title' => '',
-      '!content' => '<span>foo</span>',
-    );
-
-    // We have to reset drupal_add_css between each test.
-    drupal_static_reset();
-
-    // Test basic string for maintenance page content.
-    // No page title is set, so it should default to the site name.
-    $elements = array(
-      array(
-        'name' => "#theme 'maintenance_page' with content of <span>foo</span>",
-        'value' => array(
-          '#theme' => 'maintenance_page',
-          '#content' => '<span>foo</span>',
-          '#show_messages' => FALSE,
-        ),
-        'expected' => $expected,
-        'placeholders' => $placeholders,
-      ),
-    );
-    $this->assertElements($elements);
-
-    // Test render array for maintenance page content.
-    drupal_static_reset();
-    $elements[0]['name'] = "#theme 'maintenance_page' with content as a render array";
-    $elements[0]['value']['#content'] = array('#markup' => '<span>foo</span>');
-    // Testing with a page title, which should be combined with the site name.
-    $title = t('A non-empty title');
-    $elements[0]['value']['#page']['#title'] = $title;
-    $elements[0]['placeholders']['!title'] = '<h1>' . $title . '</h1>';
-    $elements[0]['placeholders']['!head_title'] = strip_tags($title) . ' | ' . String::checkPlain($site_config->get('name'));
-    $this->assertElements($elements);
+    ), '<meta name="description" content="Drupal test" />' . "\n", "#type 'html_tag' auto-closure meta tag generation");
+
+    // Test title tag generation.
+    $this->assertElements(array(
+      '#type' => 'html_tag',
+      '#tag' => 'title',
+      '#value' => 'title test',
+    ), "<title>title test</title>\n", "#type 'html_tag' title tag generation");
   }
 
 }