def test_get_missing_key(d):
assume('key' not in d)
with pytest.raises(KeyError):
d['key']
assert d.get('key') == Nothing()
def test_maybe_decorater(self):
maybe_int = maybe(int)
assert maybe_int('1') == Just(1)
assert maybe_int('whoops') == Nothing()
def test_nothing_bool(self):
assert not bool(Nothing())
def test_nothing_or_else(self, value):
assert Nothing().or_else(value) is value
def test_composition_law(self, f: Unary, g: Unary, value):
h = compose(f, g)
assert Just(value).map(h) == Just(value).map(g).map(f)
assert Nothing().map(h) == Nothing().map(g).map(f)
def _test_nothing_identity_law(self):
assert Nothing().map(identity) == Nothing()
def _test_just_inequality(self, value):
assert Just(value) != Nothing()
def _test_nothing_equality(self):
assert Nothing() == Nothing()