ElementsContainerTest.php

<?php

declare (strict_types=1);
namespace Drupal\Tests\system\Functional\Form;

use Drupal\Tests\BrowserTestBase;
use PHPUnit\Framework\Attributes\Group;
use PHPUnit\Framework\Attributes\RunTestsInSeparateProcesses;

/**
 * Tests the container form element for expected behavior.
 */
class ElementsContainerTest extends BrowserTestBase {
  
  /**
   * {@inheritdoc}
   */
  protected static $modules = [
    'form_test',
  ];
  
  /**
   * {@inheritdoc}
   */
  protected $defaultTheme = 'stark';
  
  /**
   * Tests the #optional container property.
   */
  public function testOptionalContainerElements() : void {
    $this->drupalGet('form-test/optional-container');
    $assertSession = $this->assertSession();
    $assertSession->elementNotExists('css', 'div.empty_optional');
    $assertSession->elementExists('css', 'div.empty_non_optional');
    $assertSession->elementExists('css', 'div.nonempty_optional');
    $assertSession->elementExists('css', 'div.nonempty_non_optional');
  }

}