Webform test teardown deletes nodes that should NOT be deleted

The teardown method in tests/webform.test removes all nodes for a certain user ID and then deletes the user account. Somehow, running the test script as user 1 all nodes that do not belong to user 1 are deleted regardless of their type.

I tried a fix of the query:

foreach ($this->webform_users as $user) {
  $uid = $user->uid;
  $result = db_query('SELECT nid FROM {node} WHERE uid = %d', $uid);
  while ($node = db_fetch_array($result)) {
    node_delete($node['nid']);
  }
  user_delete(array(), $uid);
}

to

foreach ($this->webform_users as $user) {
  $uid = $user->uid;
  $result = db_query("SELECT nid FROM {node} WHERE uid = %d AND type = '%s'", $uid, 'webform');
  while ($node = db_fetch_array($result)) {
    node_delete($node['nid']);
  }
  user_delete(array(), $uid);
}

but this still results in existing webform nodes with uid 3 to be deleted.

I'll try to retrieve the cause to this and will report anything I find. Thanks in advance for any fixes!