[cuddlybacon]

I guess the hesitation I have is a do all that, and find out the real implementation should have just been something like adding a new field to an enum and adding/adjusting some if statements.

It seems like a giant waste to build an api, when the there is one I could just extend. But to confirm I can just extend that api, I'd need to first implement the change to see it works.

[mitjak]

right, i'm talking about implementing something new. if you're trying to refactor or alter an existing codebase, it can be even easier: you add another test to an already existing suite.

i don't think i've ever sat down, written tests for a completely new implementation, only to find that i need to add a field somewhere. before i sit down to write tests, i do some preliminary thinking. i'm not saying, write tests without ever trying to think first. but do use tests to flesh out your change from outside of the black box.