listDirectories example

  protected $defaultTheme = 'stark';

  /** * Tests that all Core help topics can be rendered and have good syntax. */
  public function testHelpTopics() {
    $this->drupalLogin($this->rootUser);

    // Enable all modules and themes, so that all routes mentioned in topics     // will be defined.     $module_directories = $this->listDirectories('module');
    $modules_to_install = array_keys($module_directories);
    \Drupal::service('module_installer')->install($modules_to_install);
    $theme_directories = $this->listDirectories('theme');
    \Drupal::service('theme_installer')->install(array_keys($theme_directories));

    $directories = $module_directories + $theme_directories +
      $this->listDirectories('profile');
    $directories['core'] = \Drupal::root() . '/core/help_topics';
    $directories['bad_help_topics'] = \Drupal::service('extension.list.module')->getPath('help_topics_test') . '/bad_help_topics/syntax/';

    // Filter out directories outside of core. If you want to run this test