Issue #3371937 by yash.rode, Abhijith S, smustgrave, fgm: Theme declaration...

      'variables' => ['items' => [], 'title' => '', 'list_type' => 'ul', 'wrapper_attributes' => [], 'attributes' => [], 'empty' => NULL, 'context' => []],

    ],

    'feed_icon' => [

      'variables' => ['url' => NULL, 'title' => NULL],

      'variables' => ['url' => NULL, 'title' => NULL, 'attributes' => []],

    ],

    'progress_bar' => [

      'variables' => ['label' => NULL, 'percent' => NULL, 'message' => NULL],

    $this->assertEquals('Subscribe to <>&"'', trim(strip_tags($text)), 'feed_icon template escapes reserved HTML characters.');

  }

  /**

   * Tests that the rendered output contains specific attributes.

   */

  public function testAttributeAdded(): void {

    $variables = [

      '#theme' => 'feed_icon',

      '#url' => 'node/add/',

      '#title' => 'testing title',

      '#attributes' => ['title' => 'some title', 'class' => ['some-class']],

    ];

    $rendered_output = (string) \Drupal::service('renderer')->renderRoot($variables);

    // Check if the class 'some-class' is present in the rendered output.

    $this->assertStringContainsString('some-class', $rendered_output, "The class 'some-class' should be present in the rendered output.");

  }

}