I find it makes sense if you can write the tests at a high enough level and the tooling to mock the "outside world" of your system is easy enough to use. If yo

I find it makes sense if you can write the tests at a high enough level and the tooling to mock the "outside world" of your system is easy enough to use. If you're doing TDD exclusively with unit tests I find it falls flat for pretty much everything except complex, logical code with no state and simple inputs and outputs. Likewise I tried doing TDD on code which had complex, hard to mock interfaces to the outside world (e.g. interfacing with a horrible oracle system) and it didnt exactly become impossible but it definitely stopped being worthwhile.