def test_inversion_on_zero_amount(self):
m = Money(0, 'USD')
expected = Money(0, 'USD')
actual = m.get_inverse()
assert expected == actual
def test_inversion_on_negative_amount(self):
m = Money(-500, 'USD')
expected = Money(500, 'USD')
actual = m.get_inverse()
assert expected == actual
