public function merge_test_data($session_id, $user_id, $user_agent, $ip, $time = 0)
{
$this->set_cookies(array('_sid' => $session_id, '_u' => $user_id));
$this->merge_config_data(array('session_length' => time() + $time));
$this->merge_server_data(array('HTTP_USER_AGENT' => $user_agent, 'REMOTE_ADDR' => $ip));
}