BaseThemeRequiredTest.php

<?php

declare (strict_types=1);
namespace Drupal\KernelTests\Core\Theme;

use Drupal\KernelTests\KernelTestBase;

/**
 * Tests the behavior of the `base theme` key.
 *
 * @group Theme
 */
class BaseThemeRequiredTest extends KernelTestBase {

  /**
   * {@inheritdoc}
   */
  protected static $modules = [
    'system',
  ];

  /**
   * The theme installer.
   *
   * @var \Drupal\Core\Extension\ThemeInstallerInterface
   */
  protected $themeInstaller;

  /**
   * The theme manager.
   *
   * @var \Drupal\Core\Theme\ThemeManagerInterface
   */
  protected $themeManager;

  /**
   * {@inheritdoc}
   */
  protected function setUp() : void {
    parent::setUp();
    $this->themeInstaller = $this->container
      ->get('theme_installer');
    $this->themeManager = $this->container
      ->get('theme.manager');
  }

  /**
   * Tests opting out of Stable 9 by setting the base theme to false.
   */
  public function testWildWest() {
    $this->themeInstaller
      ->install([
      'test_wild_west',
    ]);
    $this
      ->config('system.theme')
      ->set('default', 'test_wild_west')
      ->save();
    $theme = $this->themeManager
      ->getActiveTheme();

    /** @var \Drupal\Core\Theme\ActiveTheme $base_theme */
    $base_themes = $theme
      ->getBaseThemeExtensions();
    $this
      ->assertEmpty($base_themes, 'No base theme is set when a theme has opted out of using Stable 9.');
  }

}