This is actually what I really like about wiring up tests first — it forces you to ask all the questions about expected behaviour up front, rather than later. I love writing unit tests for any classes I’m writing, because it forces me to run my code ASAP, and strongly discourages me from fudging the bits which everyone else seems to care less about. (Edge cases are buggers to debug.)
Lead tech at OCSI, making data friendly for social good. Likes words. Doesn't really own a bowler hat.