[akkartik]

I think the claim is that if you don't start out writing the functions you don't start out writing the tests, and so your tests are doomed to fall behind right from the outset.

I'm not fanatical about TDD, but in my experience the trajectory of a design changes hugely based on whether or not it had tests from the start.

(I loved your comment above. Just adding some food for my own thought.)

[sheepmullet]

"I'm not fanatical about TDD, but in my experience the trajectory of a design changes hugely based on whether or not it had tests from the start."

I'm still not sold on the benefits of fine grained unit tests as compared to having more, and better, functional tests.

If the OPs 1k+ methods had a few hundred functional tests then it should be a fairly simple matter to re-factor.

In "the old days" when I wrote code from a functional spec the spec had a list of functional tests. It was usually pretty straightforward to take that list and automate it.

[akkartik]

Yeah, that's fair. The benefits of unit tests for me were always that they forced me to decompose the problem into testable/side-effect-free functions. But this thread is about questioning the value of that in the first place.

Just so long as the outer function is testable and side-effect-free.

[mercurial]

Say you have a system with components A and B. Functional tests let you have confidence that A works fine with B. The day you need to ensure A works with C, this confidence flies out of the window, because it's perfectly possible that functional tests pass solely because of a bug in B. It's not such a big issue if the surface of A and C is small, but writing comprehensive functional tests for a large, complex system can be daunting.

[mark-r]

The intro to the post has Carmack saying he now prefers to write code in a more functional style. That's exactly the side-effect-free paradigm you're looking for.

[_delirium]

Even most of the older post is focused on side-effecting functions. His main concern with the previous approach is that functions relied on outside-the-function context (global or quasi-global state is extremely common in game engines), and a huge source of bugs was that they would be called in a slightly different context than they expected. When functions depend so brittly on reading or even mutating outside state, I can see the advantage to the inline approach, where it's very carefully tracked what is done in which sequence, and what data it reads/changes, instead of allowing any of that to happen in a more "hidden" way in nests of function-call chains. If a function is pure, on the other hand, this kind of thing isn't a concern.