When adding a new user achievement using the admin interface, if you select an invalid combination of last_updated and date_earned, you will get a ValueError stating 'UserAchievementForm' has no field named 'self.date_earned'. This is not particularly informative and makes testing harder. Ideally, if you made this error, you would stay on the admin interface and be given a notification telling you why the data you attempted to enter was invalid. This problem might be solved by either changing how data validation is done in the UserAchievement model or by some specifications to the admin interface itself.