def test_no_to_list_when_circular(self):
     head = ListNode.build_circular([i for i in range(21)])
     self.assertFalse(head.to_list())
 def test_is_circular_true(self):
     head = ListNode.build_circular([i for i in range(666)])
     self.assertTrue(head.is_circular())
 def test_is_circular_three_node_true(self):
     head = ListNode.build_circular([1, 2, 3])
     self.assertTrue(head.is_circular())