def METHOD_NAME(self):
    vts = Vts()
    vts.add('id_1', name='foo')
    vts.add('id_2', name='bar')
    it = iter(vts)
    vt_id = next(it)
    self.assertIn(vt_id, ['id_1', 'id_2'])
    vt_id = next(it)
    self.assertIn(vt_id, ['id_1', 'id_2'])
    with self.assertRaises(StopIteration):
        next(it)