--- /dev/null
+<?php
+
+namespace Drupal\Tests\system\Functional\Theme;
+
+use Drupal\Tests\BrowserTestBase;
+
+/**
+ * Tests adding Twig loaders.
+ *
+ * @group Theme
+ */
+class TwigLoaderTest extends BrowserTestBase {
+
+ /**
+ * Modules to enable.
+ *
+ * @var array
+ */
+ public static $modules = ['twig_loader_test'];
+
+ /**
+ * Tests adding an additional twig loader to the loader chain.
+ */
+ public function testTwigLoaderAddition() {
+ $environment = \Drupal::service('twig');
+
+ $template = $environment->loadTemplate('kittens');
+ $this->assertEqual($template->render([]), 'kittens', 'Passing "kittens" to the custom Twig loader returns "kittens".');
+
+ $template = $environment->loadTemplate('meow');
+ $this->assertEqual($template->render([]), 'cats', 'Passing something other than "kittens" to the custom Twig loader returns "cats".');
+ }
+
+}