diff --git a/core/modules/simpletest/lib/Drupal/simpletest/Form/SimpletestSettingsForm.php b/core/modules/simpletest/lib/Drupal/simpletest/Form/SimpletestSettingsForm.php
index 24bdb85..9a17de9 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/Form/SimpletestSettingsForm.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/Form/SimpletestSettingsForm.php
@@ -25,6 +25,14 @@ public function getFormId() {
    * {@inheritdoc}
    */
   public function buildForm(array $form, array &$form_state) {
+    // Inform the user about the sites directory that must be created.
+    if (!is_dir('sites/simpletest') || !is_writable('sites/simpletest')) {
+      drupal_set_message(t('The <em>sites/simpletest</em> directory must be created and made writable for the webserver.'), 'warning');
+    }
+    else {
+      drupal_set_message(t('The <em>sites/simpletest</em> is writable by the webserver.'));
+    }
+
     $config = $this->configFactory->get('simpletest.settings');
     $form['general'] = array(
       '#type' => 'details',
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/Form/SimpletestTestForm.php b/core/modules/simpletest/lib/Drupal/simpletest/Form/SimpletestTestForm.php
index c469b52..ed4ab7f 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/Form/SimpletestTestForm.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/Form/SimpletestTestForm.php
@@ -25,6 +25,11 @@ public function getFormId() {
    * {@inheritdoc}
    */
   public function buildForm(array $form, array &$form_state) {
+    // Inform the user about the sites directory that must be created.
+    if (!is_dir('sites/simpletest') || !is_writable('sites/simpletest')) {
+      drupal_set_message(t('The <em>sites/simpletest</em> directory must be created and made writable for the webserver.'), 'warning');
+    }
+
     // JavaScript-only table filters.
     $form['filters'] = array(
       '#type' => 'container',
diff --git a/core/modules/simpletest/simpletest.install b/core/modules/simpletest/simpletest.install
index 4b940ed..c5e3616 100644
--- a/core/modules/simpletest/simpletest.install
+++ b/core/modules/simpletest/simpletest.install
@@ -154,6 +154,16 @@ function simpletest_schema() {
 }
 
 /**
+ * Implements hook_install().
+ */
+function simpletest_install() {
+  // Inform the user about the sites directory that must be created.
+  if (!is_dir('sites/simpletest') || !is_writable('sites/simpletest')) {
+    drupal_set_message(t('The <em>sites/simpletest</em> directory must be created and made writable for the webserver.'), 'warning');
+  }
+}
+
+/**
  * Implements hook_uninstall().
  */
 function simpletest_uninstall() {
diff --git a/core/modules/simpletest/simpletest.module b/core/modules/simpletest/simpletest.module
index ba3e9d5..d66e9cb 100644
--- a/core/modules/simpletest/simpletest.module
+++ b/core/modules/simpletest/simpletest.module
@@ -18,6 +18,8 @@ function simpletest_help($path, $arg) {
       $output = '';
       $output .= '<h3>' . t('About') . '</h3>';
       $output .= '<p>' . t('The Testing module provides a framework for running automated unit tests. It can be used to verify a working state of Drupal before and after any code changes, or as a means for developers to write and execute tests for their modules. For more information, see the online handbook entry for <a href="@simpletest">Testing module</a>.', array('@simpletest' => 'http://drupal.org/documentation/modules/simpletest', '@blocks' => url('admin/structure/block'))) . '</p>';
+      $output .= '<h3>' . t('Installation');
+      $output .= '<p>' . t('In order to be able to install test sites it is required that a <em>sites/simpletest</em> exists and is writable by the webserver.');
       $output .= '<h3>' . t('Uses') . '</h3>';
       $output .= '<dl>';
       $output .= '<dt>' . t('Running tests') . '</dt>';