diff --git a/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
index 44e29c2..f2b44f8 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
@@ -157,6 +157,13 @@
   protected $kernel;
 
   /**
+   * The machine names of modules to enable during setUp().
+   *
+   * @var array
+   */
+  protected $modules = array();
+
+  /**
    * Constructor for Drupal\simpletest\WebTestBase.
    */
   function __construct($test_id = NULL) {
@@ -699,15 +706,14 @@ protected function drupalLogout() {
    * default values may be incompatible with the environment in which tests are
    * being executed.
    *
-   * @param ...
-   *   List of modules to enable for the duration of the test. This can be
-   *   either a single array or a variable number of string arguments.
+   * @param array $modules
+   *   The machine names of modules to enable.
    *
    * @see Drupal\simpletest\WebTestBase::prepareDatabasePrefix()
    * @see Drupal\simpletest\WebTestBase::changeDatabasePrefix()
    * @see Drupal\simpletest\WebTestBase::prepareEnvironment()
    */
-  protected function setUp() {
+  protected function setUp(array $modules = array()) {
     global $user, $conf;
 
     // When running tests through the Simpletest UI (vs. on the command line),
@@ -825,7 +831,6 @@ protected function setUp() {
 
     // Collect modules to install.
     $class = get_class($this);
-    $modules = array();
     while ($class) {
       if (property_exists($class, 'modules')) {
         $modules = array_merge($modules, $class::$modules);