def test_should_not_be_able_to_remove_non_existing(self):
     s = OrderedSet([1, 2, 3])
     with self.assertRaises(ValueError):
         s.remove(4)
 def test_should_be_able_to_remove_existing(self):
     s = OrderedSet([1, 2, 3])
     s.remove(2)
     assert list(s) == [1, 3]