diff -u b/core/modules/help_topics/tests/src/Functional/HelpTopicsSyntaxTest.php b/core/modules/help_topics/tests/src/Functional/HelpTopicsSyntaxTest.php
--- b/core/modules/help_topics/tests/src/Functional/HelpTopicsSyntaxTest.php
+++ b/core/modules/help_topics/tests/src/Functional/HelpTopicsSyntaxTest.php
@@ -5,7 +5,6 @@
 use Drupal\Component\Discovery\DiscoveryException;
 use Drupal\Tests\BrowserTestBase;
 use Drupal\help_topics\HelpTopicDiscovery;
-use org\bovigo\vfs\vfsStream;
 
 /**
  * Verifies that all core Help topics can be rendered and comply with standards.
@@ -44,6 +43,7 @@
     $directories = $module_directories + $theme_directories +
       $this->listDirectories('profile');
     $directories['core'] = 'core/help_topics';
+    $directories['bad_help_topics'] = \Drupal::service('extension.list.module')->getPath('help_topics_test') . '/bad_help_topics/syntax/';
 
     // Verify that a few key modules, themes, and profiles are listed, so that
     // we can be certain our directory list is complete and we will be testing
@@ -60,9 +60,16 @@
     $this->assertTrue(count($definitions) > 1, 'At least 1 topic was found');
     $top_level = $this->findTopLevel($definitions);
 
-    // Test each topic for compliance with standards.
+    // Test each topic for compliance with standards, or for failing in the
+    // right way.
     foreach (array_keys($definitions) as $id) {
-      $this->verifyTopic($id, $definitions, $top_level);
+      $is_bad_topic = (strpos($id, 'bad_help_topics.') === 0);
+      if ($is_bad_topic) {
+        $this->verifyBadTopic($id, $definitions, $top_level);
+      }
+      else {
+        $this->verifyTopic($id, $definitions, $top_level);
+      }
     }
   }
 
@@ -113,8 +120,10 @@
    *   Array of all topic definitions, keyed by ID.
    * @param array $top_level
    *   Array of top-level topic definitions, keyed by ID.
+   * @param int $response
+   *   Expected response from visiting the page for the topic.
    */
-  protected function verifyTopic($id, $definitions, $top_level) {
+  protected function verifyTopic($id, $definitions, $top_level, $response = 200) {
     $definition = $definitions[$id];
 
     // Visit the URL for the topic.
@@ -122,8 +131,10 @@
 
     // Verify the title and response.
     $session = $this->assertSession();
-    $session->statusCodeEquals(200);
-    $session->titleEquals($definition['label'] . ' | Drupal');
+    $session->statusCodeEquals($response);
+    if ($response == 200) {
+      $session->titleEquals($definition['label'] . ' | Drupal');
+    }
 
     // Verify that all the related topics exist. Also check to see if any of
     // them are top-level (we will need that in the next section).
@@ -151,6 +162,7 @@
     $body = preg_replace('|\<meta.*\/\>|sU', '', $body);
     $body = preg_replace('|\{\{.*\}\}|sU', '', $body);
     $body = preg_replace('|\{\% set.*\%\}|sU', '', $body);
+    $body = trim($body);
     $this->assertNotEmpty($body, 'Topic ' . $id . ' Twig file contains some text outside of meta tags');
 
     // Verify that if we remove all the translated text, whitespace, and
@@ -185,6 +197,62 @@
       }
     }
   }
+
+  /**
+   * Verifies that a bad topic fails in the expected way.
+   *
+   * @param string $id
+   *   ID of the topic to verify. It should start with "bad_help_topics.".
+   * @param array $definitions
+   *   Array of all topic definitions, keyed by ID.
+   * @param array $top_level
+   *   Array of top-level topic definitions, keyed by ID.
+   */
+  protected function verifyBadTopic($id, $definitions, $top_level) {
+    $bad_topic_type = substr($id, 16);
+    // Topics should fail verifyTopic() in specific ways.
+    try {
+      $this->verifyTopic($id, $definitions, $top_level, 404);
+    }
+    catch (\PHPUnit_Framework_Error_Warning $e) {
+      // The bad HTML topic fails PHP DOM parsing, which throws a PHP warning.
+      $this->assertTrue($bad_topic_type == 'bad_html');
+      $this->assertTrue(strpos($e->getMessage(), 'Unexpected end tag') !== FALSE);
+    }
+    catch (\PHPUnit_Framework_ExpectationFailedException $e) {
+      // The other bad topics fail assertions.
+      $message = $e->getMessage();
+      switch ($bad_topic_type) {
+        case 'related':
+          $this->assertTrue(strpos($message, 'only related to topics that exist') !== FALSE);
+          break;
+
+        case 'top_level':
+          $this->assertTrue(strpos($message, 'is either top-level or related to at least one other top-level topic') !== FALSE);
+          break;
+
+        case 'empty':
+          $this->assertTrue(strpos($message, 'contains some text outside of meta tags') !== FALSE);
+          break;
+
+        case 'translated':
+          $this->assertTrue(strpos($message, 'Twig file has all of its text translated') !== FALSE);
+          break;
+
+        case 'h1':
+          $this->assertTrue(strpos($message, 'has no H1 tag') !== FALSE);
+          break;
+
+        case 'hierarchy':
+          $this->assertTrue(strpos($message, 'has the correct H2-H6 heading hierarchy') !== FALSE);
+          break;
+
+        default:
+          // This was an unexpected error.
+          throw $e;
+      }
+    }
+  }
 
   /**
    * Lists the extension help topic directories of a certain type.
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/help_topics/tests/modules/help_topics_test/bad_help_topics/syntax/bad_help_topics.bad_html.html.twig
@@ -0,0 +1,3 @@
+<meta name="help_topic:top_level" content="" />
+<meta name="help_topic:label" content="Help topic with bad HTML syntax" />
+<p>{% trans %}Body goes here{% endtrans %}</h3>
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/help_topics/tests/modules/help_topics_test/bad_help_topics/syntax/bad_help_topics.empty.html.twig
@@ -0,0 +1,2 @@
+<meta name="help_topic:top_level" content="" />
+<meta name="help_topic:label" content="Help topic containing no body" />
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/help_topics/tests/modules/help_topics_test/bad_help_topics/syntax/bad_help_topics.h1.html.twig
@@ -0,0 +1,3 @@
+<meta name="help_topic:top_level" content="" />
+<meta name="help_topic:label" content="Help topic with H1 header" />
+<h1>{% trans %}Body goes here{% endtrans %}</h1>
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/help_topics/tests/modules/help_topics_test/bad_help_topics/syntax/bad_help_topics.hierarchy.html.twig
@@ -0,0 +1,3 @@
+<meta name="help_topic:top_level" content="" />
+<meta name="help_topic:label" content="Help topic with h3 without an h2" />
+<h3>{% trans %}Body goes here{% endtrans %}</h3>
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/help_topics/tests/modules/help_topics_test/bad_help_topics/syntax/bad_help_topics.related.html.twig
@@ -0,0 +1,4 @@
+<meta name="help_topic:top_level" content="" />
+<meta name="help_topic:label" content="Help topic related to nonexistent topic" />
+<meta name="help_topic:related" content="this.is.not.a.valid.help_topic.id" />
+<p>{% trans %}Body goes here{% trans %}</p>
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/help_topics/tests/modules/help_topics_test/bad_help_topics/syntax/bad_help_topics.top_level.html.twig
@@ -0,0 +1,2 @@
+<meta name="help_topic:label" content="Help topic not top level or related to top level" />
+<p>{% trans %}Body goes here{% endtrans %}</p>
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/help_topics/tests/modules/help_topics_test/bad_help_topics/syntax/bad_help_topics.translated.html.twig
@@ -0,0 +1,3 @@
+<meta name="help_topic:top_level" content="" />
+<meta name="help_topic:label" content="Help topic with untranslated text" />
+<p>Body goes here</p>
only in patch2:
unchanged:
--- a/core/modules/help_topics/tests/src/Unit/HelpTopicDiscoveryTest.php
+++ b/core/modules/help_topics/tests/src/Unit/HelpTopicDiscoveryTest.php
@@ -34,7 +34,7 @@ public function testDiscoveryExceptionProviderMismatch() {
     $discovery = new HelpTopicDiscovery(['foo' => vfsStream::url('root/modules/foo/help_topics')]);
 
     $this->expectException(DiscoveryException::class);
-    $this->expectExceptionMessage("vfs://root/modules/foo/help_topics/test.topic.html.twig should begin with 'foo.'");
+    $this->expectExceptionMessage("vfs://root/modules/foo/help_topics/test.topic.html.twig file name should begin with 'foo'");
     $discovery->getDefinitions();
   }