Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

core/modules/simpletest/src/Tests/FolderTest.php

@@ -0,0 +1,31 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\simpletest\Tests\FolderTest.
+ */
+
+namespace Drupal\simpletest\Tests;
+
+use Drupal\simpletest\WebTestBase;
+
+/**
+ * This test will check SimpleTest's treatment of hook_install during setUp.
+ * Image module is used for test.
+ *
+ * @group simpletest
+ */
+class FolderTest extends WebTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = array('image');
+
+  function testFolderSetup() {
+    $directory = file_default_scheme() . '://styles';
+    $this->assertTrue(file_prepare_directory($directory, FALSE), 'Directory created.');
+  }
+}