def test_is_coupon_available(self, start_datetime, end_datetime, timezone_now, coupon_available):
"""
Verify `is_coupon_available` return correct value.
"""
coupon = self.create_coupon(start_datetime=start_datetime, end_datetime=end_datetime)
with patch.object(timezone, 'now', return_value=timezone_now):
self.assertEqual(is_coupon_available(coupon), coupon_available)
def _validate_coupon_availablity(self, coupon, message):
"""
Raise ValidationError with specified message if coupon is not available.
"""
if not is_coupon_available(coupon):
raise DRFValidationError({'error': message})
