class BlockDemoTest

class BlockDemoTest extends BrowserTestBase {
  
  /**
   * Modules to enable.
   *
   * @var array
   */
  protected static $modules = [
    'block',
  ];
  
  /**
   * {@inheritdoc}
   */
  protected $defaultTheme = 'stark';
  
  /**
   * Check for the accessibility of the admin block demo page.
   */
  public function testBlockDemo() {
    // Create administrative user.
    $admin_user = $this->drupalCreateUser([
      'administer blocks',
      'administer themes',
    ]);
    $this->drupalLogin($admin_user);
    // Confirm we have access to the block demo page for the default theme.
    $config = $this->container
      ->get('config.factory')
      ->get('system.theme');
    $default_theme = $config->get('default');
    $this->drupalGet('admin/structure/block/demo/' . $default_theme);
    $this->assertSession()
      ->statusCodeEquals(200);
    $this->assertSession()
      ->linkByHrefExists('admin/structure/block');
    $this->assertSession()
      ->linkByHrefNotExists('admin/structure/block/list/' . $default_theme);
    // All available themes in core.
    $available_themes = [
      'olivero',
      'claro',
      'stark',
    ];
    // All available themes minute minus the default theme.
    $themes = array_diff($available_themes, [
      $default_theme,
    ]);
    foreach ($themes as $theme) {
      // Install theme.
      $this->container
        ->get('theme_installer')
        ->install([
        $theme,
      ]);
      // Confirm access to the block demo page for the theme.
      $this->drupalGet('admin/structure/block/demo/' . $theme);
      $this->assertSession()
        ->statusCodeEquals(200);
      // Confirm existence of link for "Exit block region demonstration".
      $this->assertSession()
        ->linkByHrefExists('admin/structure/block/list/' . $theme);
    }
    // Confirm access to the block demo page is denied for an invalid theme.
    $this->drupalGet('admin/structure/block/demo/invalid_theme');
    $this->assertSession()
      ->statusCodeEquals(403);
  }

}