DisplayVariantTest.php

<?php

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

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

/**
 * Tests selecting a display variant.
 */
class DisplayVariantTest extends BrowserTestBase {
  
  /**
   * {@inheritdoc}
   */
  protected static $modules = [
    'display_variant_test',
  ];
  
  /**
   * {@inheritdoc}
   */
  protected $defaultTheme = 'stark';
  
  /**
   * Tests selecting the variant and passing configuration.
   */
  public function testPageDisplayVariantSelectionEvent() : void {
    // Tests that our display variant was selected, and that its configuration
    // was passed correctly. If the configuration wasn't passed, we'd get an
    // error page here.
    $this->drupalGet('<front>');
    $this->assertSession()
      ->pageTextContains('A very important, required value.');
    $this->assertSession()
      ->pageTextContains('Explicitly passed in context.');
    $this->assertSession()
      ->responseHeaderContains('X-Drupal-Cache-Tags', 'custom_cache_tag');
  }

}