def func():
return Either.Left("derp") if isLeft else Either.Right(10)
def pure(value): return Future(lambda cb: cb(Either.pure(value)))
def test_maybe_should_return_left_when_value_is_none(self): actual = Either.maybe(None) self.assertIsInstance(actual, Left)
def test_cond_should_return_left_with_error_value_when_provided(self): actual = Either.cond(lambda x: x > 0, -3, 'Value must be positive.').fold( lambda x: x, self.fail ) self.assertEqual(actual, 'Value must be positive.')
def test_cond_should_return_left_when_value_does_not_fulfill_predicate(self): actual = Either.cond(lambda x: x > 3, 2) self.assertIsInstance(actual, Left)
def test_cond_should_return_left_without_value_when_it_does_not_fulfill_predicate(self): actual = Either.cond(lambda x: len(x) > 3, 'Mu').fold( lambda x: x, self.fail ) self.assertIsNone(actual)
def test_cond_should_return_right_when_value_fulfills_predicate(self): actual = Either.cond(lambda x: x > 3, 4) self.assertIsInstance(actual, Right)
def test_cond_should_return_right_with_value_when_it_fulfills_predicate(self): actual = Either.cond(lambda x: len(x) > 3, 'Twilight Sparkle').fold( self.fail, lambda x: x ) self.assertEqual(actual, 'Twilight Sparkle')
def test_try_except_should_pass_params_to_computation(self): actual = Either.try_except(lambda x: x, 'potato').fold( self.fail, lambda x: x ) self.assertEqual(actual, 'potato')
def test_try_except_should_return_right_when_computation_does_not_throw(self): actual = Either.try_except(lambda: 3) self.assertIsInstance(actual, Right)
def test_try_except_should_return_value_when_computation_does_not_throw(self): actual = Either.try_except(lambda: 3).fold( self.fail, lambda x: x ) self.assertEqual(actual, 3)
def test_maybe_should_put_value_in_right(self):
actual = Either.maybe('ponies').fold(
self.fail,
lambda x: x
)
self.assertEqual(actual, 'ponies')
def test_maybe_should_return_right_when_value_exists(self): actual = Either.maybe(3) self.assertIsInstance(actual, Right)