- Developer A writes a new test and gets a red bar.
- Developer B implements the code to get to a green bar.
- Developer B writes the next test.
- Developer A implements it.
And of course you’re allowed to refactor where ever reasonable. I hadn’t thought about this in respect to pairing up with my developers as I try to get them hooked on TDD, but it seems a very good pattern for learning how the process works. And of course it becomes sort of a fun competitive game.