php doctest helper: getting an authenticated user instance

docTestHelper.php

/**
 * #test test_user
 * <code>
 * #diag('expect error');
 * try {
 *   $u = test_user('peko');
 *   #fail('should raise error');
 * }
 * catch(Exception $e) {
 *   #ok($e,$e->getMessage());  
 * }
 * #diag("exipect ok");
 * #ok($u = test_user(), "ok");
 * #isa_ok($u, 'myUser', 'myUser');
 * #is($u->getUserId(), 1);
 * #is($u->getUsername(), 'john');
 * </code>
 */
function test_user($username='john', $pwd='hoge')
{
  $error = ""; $con = sfContext::getInstance();
  $con->getRequest()->setParameter('password', $pwd);
  
  $validator = new sfGuardUserValidator; 
  $validator->initialize($con);
  $validator->execute($username, $error);
  $u = $con->getUser();
  if (strlen($error) > 0) {
    throw new sfException('failed to authenticate, test user has missed: '. $error);
  }
  return $u;
}