trait AwaitTrait in Lightning Core 8.4

trait AwaitTrait {

  /**
   * Waits for a JavaScript condition to become true.
   *
   * @param string $expression
   *   The JavaScript expression to wait for.
   * @param int $timeout
   *   (optional) How long, in seconds, to wait before timing out.
   */
  protected function awaitExpression($expression, $timeout = 10) {
    try {
      $this
        ->getSession()
        ->wait($timeout * 1000, $expression);
    } catch (UnsupportedDriverActionException $e) {
      sleep($timeout);
    }
  }

  /**
   * Waits for an element to exist.
   *
   * @param string $selector
   *   The element's CSS selector.
   * @param int $timeout
   *   (optional) How long, in seconds, to wait before timing out.
   *
   * @return \Behat\Mink\Element\NodeElement
   *   The awaited element.
   */
  protected function awaitElement($selector, $timeout = 10) {
    $js = 'document.querySelector("' . addslashes($selector) . '")';
    $this
      ->awaitExpression($js, $timeout);
    return $this
      ->assertSession()
      ->elementExists('css', $selector);
  }

  /**
   * Waits for AJAX to finish.
   *
   * If the Mink context is unavailable, or the current driver does not support
   * waiting for a JavaScript condition, waits $timeout seconds and returns.
   *
   * @param int $timeout
   *   (optional) How many seconds to wait.
   */
  protected function awaitAjax($timeout = 10) {

    /** @var \Drupal\DrupalExtension\Context\MinkContext $context */
    $context = $this
      ->getContext(MinkContext::class);
    if ($context) {
      try {
        return $context
          ->iWaitForAjaxToFinish();
      } catch (UnsupportedDriverActionException $e) {

        // Fall through to sleep().
      }
    }
    sleep($timeout);
  }

}