Index: modules/user/user.test
===================================================================
RCS file: /cvs/drupal/drupal/modules/user/user.test,v
retrieving revision 1.47
diff -u -r1.47 user.test
--- modules/user/user.test	20 Jul 2009 18:51:35 -0000	1.47
+++ modules/user/user.test	25 Jul 2009 21:23:56 -0000
@@ -1016,7 +1016,7 @@
   private function insertSession(array $fields = array()) {
     $fields += array(
       'uid' => 0,
-      'sid' => md5(microtime()),
+      'sid' => md5(uniqid(mt_rand(), TRUE)),
       'timestamp' => REQUEST_TIME,
     );
     db_insert('sessions')