def test_conditionals(self, Maybe):
x = Maybe.Just(42)
assert x.just
assert not x.nothing
y = Maybe.Nothing
assert y.nothing
assert not y.just
def test_adt_has_correct_type(self, Maybe):
x = Maybe.Just(42)
y = Maybe.Nothing
assert type(x) is Maybe
assert type(y) is Maybe
assert isinstance(x, Union)
assert isinstance(y, Union)
assert issubclass(Maybe, Union)
def test_match_function_constructor(self, Maybe):
x = Maybe.Just(42)
y = Maybe.Nothing
func = Maybe.match_fn(
just=lambda x: x * 2,
nothing=lambda: 0,
)
assert func(x) == 84
assert func(y) == 0
def test_can_access_state_args_attribute(self, Maybe):
x = Maybe.Just(42)
y = Maybe.Nothing
assert x.just_args == (42, )
assert y.nothing_args == ()
with pytest.raises(AttributeError):
assert x.nothing_args
with pytest.raises(AttributeError):
assert y.just_args
def test_match_function(self, Maybe):
x = Maybe.Just(42)
y = Maybe.Nothing
res = x.match(
just=lambda x: x * 2,
nothing=lambda: 0,
)
assert res == 84
res = y.match(
just=lambda x: x * 2,
nothing=lambda: 0,
)
assert res == 0
def just(self, Maybe):
return Maybe.Just(42)
def test_to_maybe(self, ok, err):
assert ok.to_maybe() == Maybe.Just(42)
assert err.to_maybe() == Maybe.Nothing
def test_maybe_function_conversions(self, Maybe):
assert maybe(42) == Maybe.Just(42)
assert maybe(None) == Maybe.Nothing
def test_bitwise(self):
x = Maybe.Just(42)
y = Maybe.Nothing
assert x & y == y
assert x | y == x
def test_call(self):
x = Maybe.Just(42)
y = Maybe.Nothing
assert Maybe.call(lambda x, y: x + y, x, x) == Maybe.Just(84)
assert Maybe.call(lambda x, y: x + y, x, y) == Maybe.Nothing
def test_then_method(self):
x = Maybe.Just(1)
y = x.then(lambda x: x + 1).then(lambda x: x + 1)
assert y.just
assert y.value == 3
def test_adt_has_hash(self, Maybe):
assert hash(Maybe.Nothing) != hash(Maybe.Just(1))
def test_adt_matches_instance(self, Maybe):
a = Maybe.Just(42)
b = Maybe.Nothing
assert a.match(just=lambda x: x, nothing=lambda: 0) == 42
assert b.match(just=lambda x: x, nothing=lambda: 0) == 0
def test_equality(self, Maybe):
x = Maybe.Just(42)
y = Maybe.Nothing
assert y == Maybe.Nothing
assert x == Maybe.Just(42)
assert x != y
def test_adt_repr(self, Maybe):
assert repr(Maybe.Just(42)) == 'Just(42)'
assert repr(Maybe.Nothing) == 'Nothing'
def test_adt_requires_correct_number_of_arguments(self, Maybe):
with pytest.raises(TypeError):
Maybe.Just(1, 2)
with pytest.raises(TypeError):
Maybe.Just()
def test_maybe_chaining(self):
x = (Maybe.Just(42) >> (lambda x: 2 * x)).get()
y = (Maybe.Nothing >> (lambda x: 2 * x)).get()
assert x == 84
assert y == None
