def test_numbers_unique(self): number1 = get_random_phone_number() number2 = str(1 + long(number1)) reg = RegistrationCenterFactory() StaffPhone.objects.create(phone_number=number1, registration_center=reg) StaffPhone.objects.create(phone_number=number2, registration_center=reg) obj = StaffPhone(phone_number=number2, registration_center=reg) with self.assertRaises(ValidationError): obj.clean()