class LayoutPluginManagerTest

class LayoutPluginManagerTest extends KernelTestBase {
  
  /**
   * {@inheritdoc}
   */
  protected static $modules = [
    'layout_discovery',
  ];
  
  /**
   * {@inheritdoc}
   */
  protected function setUp() : void {
    parent::setUp();
    $this->container
      ->get('theme_installer')
      ->install([
      'test_child_theme',
    ]);
    $this->activateTheme('test_child_theme');
  }
  
  /**
   * Tests that layout plugins are correctly overridden.
   */
  public function testPluginOverride() : void {
    /** @var \Drupal\Core\Layout\LayoutPluginManagerInterface $layouts_manager */
    $layouts_manager = $this->container
      ->get('plugin.manager.core.layout');
    $definitions = $layouts_manager->getDefinitions();
    $this->assertInstanceOf(LayoutDefinition::class, $definitions['theme_parent_provided_layout']);
    $this->assertSame('Child', $definitions['theme_parent_provided_layout']->getLabel()
      ->render());
  }
  
  /**
   * Activates a specified theme.
   *
   * Installs the theme if not already installed and makes it the active theme.
   *
   * @param string $theme_name
   *   The name of the theme to be activated.
   */
  protected function activateTheme(string $theme_name) : void {
    $this->container
      ->get('theme_installer')
      ->install([
      $theme_name,
    ]);
    /** @var \Drupal\Core\Theme\ThemeInitializationInterface $theme_initializer */
    $theme_initializer = $this->container
      ->get('theme.initialization');
    /** @var \Drupal\Core\Theme\ThemeManagerInterface $theme_manager */
    $theme_manager = $this->container
      ->get('theme.manager');
    $theme_manager->setActiveTheme($theme_initializer->getActiveThemeByName($theme_name));
    $this->assertSame($theme_name, $theme_manager->getActiveTheme()
      ->getName());
  }

}