I don't think you understand the significance of the word "driven." Coding something and then testing it is not TDD. In TDD, you don't write any application code that a failed test doesn't demand in order to pass—and even then, only just enough to make that test pass, even if it just means alwars returning 4 from a rand function.

Of course, a "play test" is not an unit test, or an integration test (and is only mildly similar to an acceptance test.) Playtest-driven development would be an entirely new affair, likely involving gameplay freeze-states and kept in version control, and a constant numerical analysis for the player's emotional state (perhaps using some sort of face-recognition) given alternate code paths.