diff --git a/core/modules/help_topics/tests/src/Kernel/HelpTopicCoreTopicsTest.php b/core/modules/help_topics/tests/src/Kernel/HelpTopicCoreTopicsTest.php
index 6ca6eb4929..4ad4579323 100644
--- a/core/modules/help_topics/tests/src/Kernel/HelpTopicCoreTopicsTest.php
+++ b/core/modules/help_topics/tests/src/Kernel/HelpTopicCoreTopicsTest.php
@@ -149,16 +149,29 @@ protected function verifyTopic($id) {
     $text = preg_replace('|\s+|', '', $text);
     $this->assertTrue(empty($text), 'Topic ' . $id . ' Twig file contains only translated text');
 
-    // Verify that there is not an H1 tag.
-    $this->assertTrue(strpos($body, '<h1') === FALSE, 'Topic ' . $id . ' has no H1 tag');
-
-    // Verify the proper hierarchy of other heading tags -- there should only
-    // be an H3 if there is an H2, etc.
-    $has_heading[1] = TRUE;
-    foreach ([2, 3, 4, 5, 6] as $num) {
-      $has_heading[$num] = (strpos($body, '<h' . $num) !== FALSE);
-      $this->assertTrue($has_heading[$num - 1] || !$has_heading[$num],
-        'Topic ' . $id . ' has the correct H2-H6 heading hierarchy');
+    // Load the topic body as HTML and verify that it parses.
+    $doc = new \DOMDocument();
+    $doc->strictErrorChecking = TRUE;
+    $doc->validateOnParse = TRUE;
+    $doc->loadHTML($body);
+
+    // Check for headings hierarchy.
+    $levels = [1, 2, 3, 4, 5, 6];
+    foreach ($levels as $level) {
+      $num_headings[$level] = $doc->getElementsByTagName('h' . $level)->length;
+      if ($level == 1) {
+        $this->assertTrue($num_headings[1] == 0, 'Topic ' . $id . ' has no H1 tag');
+        // Set num_headings to 1 for this level, so the rest of the hierarchy
+        // can be tested using simpler code.
+        $num_headings[1] = 1;
+      }
+      else {
+        // We should either not have this heading, or if we do have one at this
+        // level, we should also have the next-smaller level. That is, if we
+        // have an h3, we should have also had an h2.
+        $this->assertTrue($num_headings[$level - 1] > 0 || $num_headings[$level] == 0,
+          'Topic ' . $id . ' has the correct H2-H6 heading hierarchy');
+      }
     }
   }