diff --git a/core/modules/simpletest/src/BrowserTestBase.php b/core/modules/simpletest/src/BrowserTestBase.php
index dc933ac..b314e07 100644
--- a/core/modules/simpletest/src/BrowserTestBase.php
+++ b/core/modules/simpletest/src/BrowserTestBase.php
@@ -1232,27 +1232,20 @@ protected function rebuildContainer() {
    *   The mocked request object.
    */
   protected function prepareRequestForGenerator($clean_urls = TRUE, $override_server_vars = array()) {
+    // Use a request object to gather server variables and base path.
     $request = Request::createFromGlobals();
-    $server = $request->server->all();
-    if (basename($server['SCRIPT_FILENAME']) != basename($server['SCRIPT_NAME'])) {
-      // We need this for when the test is executed by run-tests.sh.
-      // @todo Remove this once run-tests.sh has been converted to use a Request
-      //   object.
-      $cwd = getcwd();
-      $server['SCRIPT_FILENAME'] = $cwd . '/' . basename($server['SCRIPT_NAME']);
-      $base_path = rtrim($server['REQUEST_URI'], '/');
-    }
-    else {
-      $base_path = $request->getBasePath();
-    }
+    $server = array_merge($request->server->all(), $override_server_vars);
+
+    // Manipulate the base path based on $clean_urls.
+    $base_path = $request->getBasePath();
     if ($clean_urls) {
       $request_path = $base_path ? $base_path . '/user' : 'user';
     }
     else {
       $request_path = $base_path ? $base_path . '/index.php/user' : '/index.php/user';
     }
-    $server = array_merge($server, $override_server_vars);
 
+    // Build a new request object with our new path and server variables.
     $request = Request::create($request_path, 'GET', array(), array(), array(), $server);
     // Ensure the request time is REQUEST_TIME to ensure that API calls
     // in the test use the right timestamp.