def test_add_two_none(self): assert_that(add(None, None), equal_to(0.0))
def test_add_two_normal(self): assert_that(add(5.1, 6.2), equal_to(11.3))
def test_add_right_none(self): assert_that(add(5.0, None), equal_to(5.0))
def test_add_left_none(self): assert_that(add(None, 5.0), equal_to(5.0))
def test_add_two_nan(self): assert_that(add(NaN, NaN), equal_to(0.0))
def test_add_right_nan(self): assert_that(add(5.0, NaN), equal_to(5.0))
def test_add_left_nan(self): assert_that(add(NaN, 5.0), equal_to(5.0))