def test_isjust_isnothing():
j = Maybe.from_nullable(42)
n = Maybe.from_nullable(None)
assert j.isjust
assert not j.isnothing
assert not n.isjust
assert n.isnothing
def test_fmap():
double = lambda x: x * 2
assert Maybe.of(21).fmap(double)._value == 42
assert Maybe.from_nullable(None).fmap(double)._value == None
def test_chain():
add1 = lambda x: x + 1
assert Maybe.from_nullable(41).chain(add1) == 42
assert Maybe.from_nullable(None).chain(add1) == None
def test_join():
assert Maybe.from_nullable(42).join() == 42
assert Maybe.from_nullable(None).join() == None
def test_of():
assert Maybe.of(42)._value == 42
def test_ap():
add = lambda x: lambda y: x + y
assert Maybe.from_nullable(add).ap(Maybe.of(3)).ap(
Maybe.of(39))._value == 42
assert Maybe.from_nullable(None).ap(Maybe.of(3)).ap(
Maybe.of(39))._value == None
def test_inspect():
assert Maybe.of("hello, world").inspect() == "Just(hello, world)"
assert Maybe.from_nullable(None).inspect() == "Nothing()"