def test_contains(container):
item = object()
added = s.contains_add(container, item)
assert isinstance(added, type(container))
assert item in added
removed = s.contains_remove(added, item)
assert isinstance(removed, type(container))
assert item not in removed
def _lens_contains_add(self, item):
return Box(s.contains_add(self.value, item))
def test_contains_add_failure():
with pytest.raises(NotImplementedError):
s.contains_add(True, object())