- Your class can be no longer than a hundred lines of code.
- Your methods can be no longer than five lines of code
- You can pass no more than four parameters and you can't just make it one big hash.
- In your controller, you can only instantiate one object, to do whatever it is that needs to be done.
- Your view can only know about one instance variable.
- Your Rails view should only send messages to that object i.e., no Demeter violations.[ "thunder dome principal". Translated: one model in, one model out! ]
- Rules are meant to be broken if by breaking them you produce better code. [ ...where "better code" is validated by explaining why you want to break the rule to someone else. ]
- Make assertions about state for incoming messages.
- Make assertions that you send outgoing messages. [Only do #2 for outgoing /command/ messages. Don't bother testing query methods at all, though you may need to stub those to make your tests work right.]
- Ignore private methods.
- Test roles. Make tests prove they are playing the correct role (and not just testing the mock / double)
