symfony, test and sf_user attributes

It is surprisingly hard to change the attributes of the user session in a functionnal test. Suppose you want to do something like

$sf_user->setAttribute('myownkey', 'myownval');

But you are in a funcitonnal test, here is how i did it

$storage = new sfSessionTestStorage(array(
 'session_path' => sfConfig::get('sf_test_cache_dir')."/sessions"
));
$storage->write('symfony/user/sfUser/attributes', array(
 'symfony/user/sfUser/attributes' => array(
  'myownkey' =>'myownval'
 )
));
$storage->shutdown();