--- /dev/null
+<?php
+
+namespace Drupal\FunctionalTests\Theme;
+
+use Drupal\Tests\BrowserTestBase;
+
+/**
+ * Tests the classy theme.
+ *
+ * @group classy
+ */
+class ClassyTest extends BrowserTestBase {
+
+ /**
+ * {@inheritdoc}
+ */
+ public function setUp() {
+ parent::setUp();
+
+ $this->assertTrue($this->container->get('theme_installer')->install(['classy']));
+ $this->container->get('config.factory')
+ ->getEditable('system.theme')
+ ->set('default', 'classy')
+ ->save();
+ }
+
+ /**
+ * 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');
+ }
+
+}