=== modified file 'includes/database.inc'
--- includes/database.inc	(revision 611)
+++ includes/database.inc	(working copy)
@@ -637,6 +637,8 @@
    * @param $target
    */
   final protected static function openConnection($key, $target) {
+    global $db_prefix;
+
     if (empty(self::$connectionInfo)) {
       self::parseConnectionInfo();
     }
@@ -660,6 +662,12 @@
       $driver_file ='./includes/database.'. $driver .'.inc';
       require_once($driver_file);
       self::$connections[$key][$target] = new $driver_class(self::$databaseInfo[$key][$target]);
+
+      // We need to pass around the simpletest database prefix in the request
+      // and we put that in the user_agent header.
+      if (preg_match("/^simpletest\d+$/", $_SERVER['HTTP_USER_AGENT'])) {
+        $db_prefix = $_SERVER['HTTP_USER_AGENT'];
+      }
     }
     catch (Exception $e) {
       _db_need_install();