ClassyTest.php

<?php

namespace Drupal\FunctionalTests\Theme;

use Drupal\Tests\BrowserTestBase;

/**
 * Tests the classy theme.
 *
 * @group classy
 */
class ClassyTest extends BrowserTestBase {
    
    /**
     * {@inheritdoc}
     */
    protected $defaultTheme = 'classy';
    
    /**
     * Tests that the Classy theme always adds its message CSS.
     *
     * @see classy.info.yml
     */
    public function testRegressionMissingMessagesCss() {
        $this->drupalGet('');
        $this->assertSession()
            ->statusCodeEquals(200);
        $this->assertSession()
            ->responseContains('classy/css/components/messages.css');
    }

}