def test_to_dot(self): a = [] b = [] a.append(b) graph = ObjectGraph([a, b]) dot = graph.to_dot() self.assertIn('{} -> {} [label="item[0]"];'.format(id(a), id(b)), dot) self.assertIn('{} [label="list[1]"];'.format(id(a)), dot) self.assertIn('{} [label="list[0]"];'.format(id(b)), dot) self.assertIsInstance(dot, six.text_type)