In my current project (a game, in C++), I decided that I would use Test Driven Development 100% during development.
In terms of code quality, this has been great. My code has never been so well designed or so bug-free. I don't cringe when viewing code I wrote a year ago at the start of the project, and I have gained a much better sense for how to structure things, not only to be more easily testable, but to be simpler to implement and use.
However... it has been a year since I started the project. Granted, I can only work on it in my spare time, but TDD is still slowing me down considerably compared to what I'm used to. I read that the slower development speed gets better over time, and I definitely do think up tests a lot more easily than I used to, but I've been at it for a year now and I'm still working at a snail's pace.
Each time I think about the next step that needs work, I have to stop every time and think about how I would write a test for it, to allow me to write the actual code. I'll sometimes get stuck for hours, knowing exactly what code I want to write, but not knowing how to break it down finely enough to fully cover it with tests. Other times, I'll quickly think up a dozen tests, and spend an hour writing tests to cover a tiny piece of real code that would have otherwise taken a few minutes to write.
Or, after finishing the 50th test to cover a particular entity in the game and all aspects of it's creation and usage, I look at my to-do list and see the next entity to be coded, and cringe in horror at the thought of writing another 50 similar tests to get it implemented.
It's gotten to the point that, looking over the progress of the last year, I'm considering abandoning TDD for the sake of "getting the damn project finished". However, giving up the code quality that came with it is not something I'm looking forward to. I'm afraid that if I stop writing tests, then I'll slip out of the habit of making the code so modular and testable.
Am I perhaps doing something wrong to still be so slow at this? Are there alternatives that speed up productivity without completely losing the benefits? TAD? Less test coverage? How do other people survive TDD without killing all productivity and motivation?