def test_Values_from_parent_are_found_via_get():
world = Env()
world.set("w", 2)
town = world.make_child()
town.set("t", 3)
house = town.make_child()
house.set("h", 4)
assert house.get("h") == 4
assert house.get("t") == 3
assert house.get("w") == 2
assert not town.contains("h")
assert not world.contains("t")
def test_After_setting_a_name_Env_contains_it():
env = Env()
env.set("myname", "foo")
assert env.contains("myname")
assert not env.contains("othername")
def test_Empty_Env_does_not_contain_names():
env = Env()
assert not env.contains("x")