def test_first_valid_second_valid_plus_calculate(self):
viewmodel = RationalNumberViewModel()
viewmodel.set_first_number("12/3")
viewmodel.set_second_number("2/7")
viewmodel.set_operation("+")
viewmodel.calculate()
self.assertEqual("30/7", viewmodel.get_result())
def test_number_updated_result_empty(self):
viewmodel = RationalNumberViewModel()
viewmodel.set_first_number("12/3")
viewmodel.set_second_number("2/7")
viewmodel.set_operation("+")
viewmodel.calculate()
viewmodel.set_first_number("12/11")
self.assertEqual("", viewmodel.get_result())