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]