class ActionsTest

class ActionsTest extends KernelTestBase implements FormInterface {
  
  /**
   * {@inheritdoc}
   */
  protected static $modules = [
    'system',
  ];
  
  /**
   * {@inheritdoc}
   */
  public function getFormId() {
    return __CLASS__;
  }
  
  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state) {
    $form['actions'] = [
      '#type' => 'actions',
    ];
    $form['actions']['key'] = [
      '#type' => 'submit',
      '#value' => 'Key',
      '#dropbutton' => 'submit',
      '#cache' => [
        'tags' => [
          'foo',
        ],
      ],
      '#attached' => [
        'library' => [
          'system/base',
        ],
      ],
    ];
    $form['actions']['submit'] = [
      '#type' => 'submit',
      '#value' => 'Save',
    ];
    return $form;
  }
  
  /**
   * {@inheritdoc}
   */
  public function validateForm(array &$form, FormStateInterface $form_state) {
  }
  
  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
  }
  public function testDropbuttonWithBubbleableMetadata() {
    $result = \Drupal::formBuilder()->getForm($this);
    \Drupal::service('renderer')->renderRoot($result);
    $this->assertEquals([
      'system/base',
      'core/drupal.dropbutton',
    ], $result['#attached']['library']);
    $this->assertEquals([
      'foo',
    ], $result['#cache']['tags']);
  }

}