class TwigRegistryLoaderTest

class TwigRegistryLoaderTest extends BrowserTestBase {

  /**
   * Modules to enable.
   *
   * @var array
   */
  protected static $modules = [
    'twig_theme_test',
    'block',
  ];

  /**
   * {@inheritdoc}
   */
  protected $defaultTheme = 'stark';

  /**
   * @var \Drupal\Core\Template\TwigEnvironment
   */
  protected $twig;

  /**
   * {@inheritdoc}
   */
  protected function setUp() : void {
    parent::setUp();
    \Drupal::service('theme_installer')
      ->install([
      'test_theme_twig_registry_loader',
      'test_theme_twig_registry_loader_theme',
      'test_theme_twig_registry_loader_subtheme',
    ]);
    $this->twig = \Drupal::service('twig');
  }

  /**
   * Checks to see if a value is a Twig template.
   *
   * @internal
   */
  public function assertTwigTemplate($value, string $message = '') : void {
    $this
      ->assertInstanceOf(TemplateWrapper::class, $value, $message);
  }

  /**
   * Tests template discovery using the Drupal theme registry.
   */
  public function testTemplateDiscovery() {
    $this
      ->assertTwigTemplate($this->twig
      ->load('block.html.twig'), 'Found block.html.twig in block module.');
  }

  /**
   * Tests template extension and includes using the Drupal theme registry.
   */
  public function testTwigNamespaces() {

    // Test the module-provided extend and insert templates.
    $this
      ->drupalGet('twig-theme-test/registry-loader');
    $this
      ->assertSession()
      ->pageTextContains('This line is from twig_theme_test/templates/twig-registry-loader-test-extend.html.twig');
    $this
      ->assertSession()
      ->pageTextContains('This line is from twig_theme_test/templates/twig-registry-loader-test-include.html.twig');

    // Enable a theme that overrides the extend and insert templates to ensure
    // they are picked up by the registry loader.
    $this
      ->config('system.theme')
      ->set('default', 'test_theme_twig_registry_loader')
      ->save();
    $this
      ->drupalGet('twig-theme-test/registry-loader');
    $this
      ->assertSession()
      ->pageTextContains('This line is from test_theme_twig_registry_loader/templates/twig-registry-loader-test-extend.html.twig');
    $this
      ->assertSession()
      ->pageTextContains('This line is from test_theme_twig_registry_loader/templates/twig-registry-loader-test-include.html.twig');

    // Enable overriding theme that overrides the extend and insert templates
    // from the base theme.
    $this
      ->config('system.theme')
      ->set('default', 'test_theme_twig_registry_loader_theme')
      ->save();
    $this
      ->drupalGet('twig-theme-test/registry-loader');
    $this
      ->assertSession()
      ->pageTextContains('This line is from test_theme_twig_registry_loader_theme/templates/twig-registry-loader-test-extend.html.twig');
    $this
      ->assertSession()
      ->pageTextContains('This line is from test_theme_twig_registry_loader_theme/templates/twig-registry-loader-test-include.html.twig');

    // Enable a subtheme for the theme that doesn't have any overrides to make
    // sure that templates are being loaded from the first parent which has the
    // templates.
    $this
      ->config('system.theme')
      ->set('default', 'test_theme_twig_registry_loader_subtheme')
      ->save();
    $this
      ->drupalGet('twig-theme-test/registry-loader');
    $this
      ->assertSession()
      ->pageTextContains('This line is from test_theme_twig_registry_loader_theme/templates/twig-registry-loader-test-extend.html.twig');
    $this
      ->assertSession()
      ->pageTextContains('This line is from test_theme_twig_registry_loader_theme/templates/twig-registry-loader-test-include.html.twig');
  }

}