diff -u b/core/modules/help_topics/tests/src/Kernel/HelpTopicCoreTopicsTest.php b/core/modules/help_topics/tests/src/Kernel/HelpTopicCoreTopicsTest.php
--- b/core/modules/help_topics/tests/src/Kernel/HelpTopicCoreTopicsTest.php
+++ b/core/modules/help_topics/tests/src/Kernel/HelpTopicCoreTopicsTest.php
@@ -3,8 +3,8 @@
 namespace Drupal\Tests\help_topics\Kernel;
 
 use Drupal\Component\Discovery\DiscoveryException;
-use Drupal\help_topics\HelpTopicDiscovery;
 use Drupal\KernelTests\KernelTestBase;
+use Drupal\help_topics\HelpTopicDiscovery;
 use org\bovigo\vfs\vfsStream;
 
 /**
@@ -13,27 +13,16 @@
  */
 class HelpTopicCoreTopicsTest extends KernelTestBase {
 
+  use HelpTopicDiscoveryHelperTrait;
+
   /**
    * Ensure all core help topics do not throw exceptions and follow standards.
    */
   public function testCoreTopics() {
 
-    $directories = [];
-
-    // Add directories for all modules, themes, and profiles, even if they are
-    // not installed, but excluding test ones.
-    foreach (['module', 'theme', 'profile'] as $type) {
-      $lister = \Drupal::service('extension.list.' . $type);
-      foreach ($lister->getAllAvailableInfo() as $name => $info) {
-        $path = $lister->getPath($name);
-        // You can tell test modules because they are in package 'Testing', but
-        // test themes are only known by being found in test directories. So...
-        // exclude things in test directories.
-        if (strpos($path, '/tests/' . $type . 's/') === FALSE) {
-          $directories[$name] = $path . '/help_topics';
-        }
-      }
-    }
+    $directories = $this->listDirectories('module') +
+      $this->listDirectories('theme') +
+      $this->listDirectories('profile');
 
     // Just to make sure, verify that a few key modules, themes, and profiles
     // are listed. If these lines fail, it is probably because something is
@@ -48,14 +37,9 @@
     $directories['core'] = 'core/help_topics';
 
     // Discover the help topics within these directories.
-    $discovery = new HelpTopicDiscovery($directories);
-    $definitions = $discovery->getDefinitions();
+    $definitions = $this->discoverAllTopics($directories);
     $this->assertTrue(count($definitions) > 1, 'At least 1 topic was found');
-
-    // Figure out which topics are top-level.
-    $top_level = array_filter($definitions, function($definition) {
-      return isset($definition['top_level']) && $definition['top_level'];
-    });
+    $top_level = $this->findTopLevel($definitions);
 
     // Test each topic for compliance with standards.
     foreach (array_keys($definitions) as $id) {
@@ -79,8 +63,7 @@
     // Check that just this expected failure topic does throw an exception.
     $this->expectException(DiscoveryException::class);
     $this->expectExceptionMessage("vfs://root/modules/test/help_topics/test.topic.html.twig should begin with 'expected_failure.'");
-    $fail_discovery = new HelpTopicDiscovery($fail_directories);
-    $fail_discovery->getDefinitions();
+    $this->discoverAllTopics($fail_directories);
   }
 
   /**
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/help_topics/tests/src/Functional/HelpTopicsRenderTest.php
@@ -0,0 +1,71 @@
+<?php
+
+namespace Drupal\Tests\help_topics\Functional;
+
+use Drupal\Tests\BrowserTestBase;
+use Drupal\Tests\help_topics\Kernel\HelpTopicDiscoveryHelperTrait;
+
+/**
+ * Verifies that all core Help topics can be rendered.
+ *
+ * @todo This test should eventually be folded into
+ * Drupal\Tests\system\Functional\Module\InstallUninstallTest
+ * when help_topics becomes stable, so that it will test with only one module
+ * at a time installed and not duplicate the effort of installing. See issue
+ * https://www.drupal.org/project/drupal/issues/3074040
+ *
+ * @group help_topics
+ */
+class HelpTopicsRenderTest extends BrowserTestBase {
+  use HelpTopicDiscoveryHelperTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = [
+    'help',
+    'help_topics',
+  ];
+
+  /**
+   * Tests that all Core help topics can be rendered.
+   */
+  public function testHelpRendering() {
+    $this->drupalLogin($this->rootUser);
+
+    // Enable all modules and themes, so that hopefully all routes will be
+    // defined.
+    $module_directories = $this->listDirectories('module');
+    $this->container->get('module_installer')->install(array_keys($module_directories));
+    $theme_directories = $this->listDirectories('theme');
+    $this->container->get('theme_installer')->install(array_keys($theme_directories));
+
+    $directories = $module_directories + $theme_directories +
+      $this->listDirectories('profile');
+    $directories['core'] = 'core/help_topics';
+
+    $definitions = $this->discoverAllTopics($directories);
+    foreach ($definitions as $id => $definition) {
+      $this->verifyTopicRendering($id, $definition);
+    }
+  }
+
+  /**
+   * Verifies rendering of one help topic.
+   *
+   * @param string $id
+   *   ID of the topic to render.
+   * @param array $definition
+   *   Definition of the topic.
+   */
+  protected function verifyTopicRendering($id, $definition) {
+    // Visit the URL for the topic.
+    $this->drupalGet('admin/help/topic/' . $id);
+
+    // Verify the title and response.
+    $session = $this->assertSession();
+    $session->statusCodeEquals(200);
+    $session->titleEquals($definition['label'] . ' | Drupal');
+  }
+
+}
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/help_topics/tests/src/Kernel/HelpTopicDiscoveryHelperTrait.php
@@ -0,0 +1,72 @@
+<?php
+
+namespace Drupal\Tests\help_topics\Kernel;
+
+use Drupal\help_topics\HelpTopicDiscovery;
+
+/**
+ * Provides a function that discovers all help topics in non-test locations.
+ */
+trait HelpTopicDiscoveryHelperTrait {
+
+  /**
+   * Lists the extension directories of a certain type.
+   *
+   * @param string $type
+   *   The type of extension to list: module, theme, or profile.
+   *
+   * @return string[]
+   *   An array of all of the directories of this type of extension, keyed by
+   *   extension short name.
+   */
+  protected function listDirectories($type) {
+    $directories = [];
+
+    // Find the extensions of this type, even if they are not installed, but
+    // excluding test ones.
+    $lister = \Drupal::service('extension.list.' . $type);
+    foreach ($lister->getAllAvailableInfo() as $name => $info) {
+      $path = $lister->getPath($name);
+      // You can tell test modules because they are in package 'Testing', but
+      // test themes are only known by being found in test directories. So...
+      // exclude things in test directories.
+      if ((strpos($path, '/tests') === FALSE) &&
+        (strpos($path, '/testing') === FALSE)) {
+        $directories[$name] = $path . '/help_topics';
+      }
+    }
+    return $directories;
+  }
+
+  /**
+   * Discovers the help topics in a list of locations.
+   *
+   * @param string[] $directories
+   *   An array of directories to find topics in, keyed by extension short name.
+   *
+   * @return array
+   *    Array of all topic definitions, keyed by topic ID, from non-test
+   *    modules, themes, and profiles.
+   */
+  protected function discoverAllTopics(array $directories) {
+    $discovery = new HelpTopicDiscovery($directories);
+    return $discovery->getDefinitions();
+  }
+
+  /**
+   * Finds the list of top-level topics.
+   *
+   * @param array $definitions
+   *   An array of topic definitions, keyed by ID.
+   *
+   * @return array
+   *   The items from $definitions that represent top-level topics, still
+   *   keyed by ID.
+   */
+  protected function findTopLevel(array $definitions) {
+    return array_filter($definitions, function($definition) {
+      return isset($definition['top_level']) && $definition['top_level'];
+    });
+  }
+
+}