diff --git a/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
index d3ba7b3..1b746e6 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
@@ -179,6 +179,20 @@
   protected $configImporter;
 
   /**
+   * A list of unique strings generated by randomString().
+   *
+   * @var array
+   */
+  protected $randomStrings = array();
+
+  /**
+   * A list of unique names generated by randomName().
+   *
+   * @var array
+   */
+  protected $randomNames = array();
+
+  /**
    * Constructor for Test.
    *
    * @param $test_id
@@ -1152,7 +1166,7 @@ protected function settingsSet($name, $value) {
   }
 
   /**
-   * Generates a random string of ASCII characters of codes 32 to 126.
+   * Generates a unique random string of ASCII characters of codes 32 to 126.
    *
    * The generated string includes alpha-numeric characters and common
    * miscellaneous characters. Use this method when testing general input
@@ -1170,16 +1184,18 @@ protected function settingsSet($name, $value) {
    *
    * @see Drupal\simpletest\TestBase::randomName()
    */
-  public static function randomString($length = 8) {
-    $str = '';
-    for ($i = 0; $i < $length; $i++) {
-      $str .= chr(mt_rand(32, 126));
-    }
+  public function randomString($length = 8) {
+    do {
+      $str = '';
+      for ($i = 0; $i < $length; $i++) {
+        $str .= chr(mt_rand(32, 126));
+      }
+    } while (isset($this->randomStrings[$str]));
     return $str;
   }
 
   /**
-   * Generates a random string containing letters and numbers.
+   * Generates a unique random string containing letters and numbers.
    *
    * The string will always start with a letter. The letters may be upper or
    * lower case. This method is better for restricted inputs that do not
@@ -1198,13 +1214,15 @@ public static function randomString($length = 8) {
    *
    * @see Drupal\simpletest\TestBase::randomString()
    */
-  public static function randomName($length = 8) {
-    $values = array_merge(range(65, 90), range(97, 122), range(48, 57));
-    $max = count($values) - 1;
-    $str = chr(mt_rand(97, 122));
-    for ($i = 1; $i < $length; $i++) {
-      $str .= chr($values[mt_rand(0, $max)]);
-    }
+  public function randomName($length = 8) {
+    do {
+      $values = array_merge(range(65, 90), range(97, 122), range(48, 57));
+      $max = count($values) - 1;
+      $str = chr(mt_rand(97, 122));
+      for ($i = 1; $i < $length; $i++) {
+        $str .= chr($values[mt_rand(0, $max)]);
+      }
+    } while (isset($this->randomNames[$str]));
     return $str;
   }
 
@@ -1218,11 +1236,11 @@ public static function randomName($length = 8) {
    *   The generated object, with the specified number of random keys. Each key
    *   has a random string value.
    */
-  public static function randomObject($size = 4) {
+  public function randomObject($size = 4) {
     $object = new \stdClass();
     for ($i = 0; $i < $size; $i++) {
-      $random_key = self::randomName();
-      $random_value = self::randomString();
+      $random_key = $this->randomName();
+      $random_value = $this->randomString();
       $object->{$random_key} = $random_value;
     }
     return $object;