[iopq]

No, like in some programs when I figure out how to do it correctly the unit tests are either complete tautologies or integration tests.

Then there are the "write once, never fail ever" tests. Okay, so the test made sense when I wrote the code. I will never touch that part ever again because it works perfectly. Why do I keep running them every time?

[lojack]

If the unit tests are tautologies then they aren't testing the right things, and if they are integration tests then they aren't actually unit tests.

I personally run my unit tests every time to confirm my assumptions that the unit of code under test hasn't changed. I also assume all code I write will inevitably be changed in the future because business requirements change and there's always room for improvement. Actually can't think of a single piece of code I've written (apart from code I've thrown out) that didn't eventually need to be rewritten. The benefit of running unit tests is less than the benefit of running integration tests, but the cost of running them is also significantly less. Current project I'm working on has 10x as many unit tests as integration tests and they run 100x faster.

My workflow is usually run my unit tests for the code I'm working on constantly, and when I think things are working run the entire test suite to verify everything works well together. Thats my workflow whether or not I'm doing TDD.

[iopq]

The code that determines truths about the data never had to be rewritten.

Like, are the two points neighbors? I mean, I'm not going to write a version of this function for a spherical board in the future. Nobody plays on a spherical board.

It's also a really boring unit test. Yes, (1,1) and (1,2) are neighbors. Do I really need to test this function until the end of time?

[lojack]

Thats exactly the type of code that should be unit tested. The unit tests are trivially easy to write, and a very naive solution is easy to code up. The tests should take up a negligible overhead in your overall test suite runtime. Then when it comes time to optimize the code because its becoming a bottleneck you can be confident that the more obscure solution is correct.