I didn't mention unit tests, so maybe you meant to respond to someone else? Or you're just shouting into the wind about something that wasn't said for fun?

I was writing about tests generally, in case you were wondering.

The comment you responded to says unit tests give confidence, you seem to agree.

"Tests generally" and unit tests are pretty much the opposite camps in testing world.

I agreed about the word "confidence" and the importance of testing for confidence. You read something into my comment that I did not write nor did I intend. Good for you, I guess.

If you can fit the entire system in your head, it's probably a relatively simple codebase.

I've written a Photoshop file format parser twice, and trust me—between byte alignment changing constantly throughout the spec, at least three different string encodings, sub-formats and errors in the spec—it does not "fit in your head." Certainly not enough to confidently add features without worrying that you've broken the blend mode parser.

And of course, if you can and do fit a complex system in your head when no one else on the team can, congratulations: you've made yourself into a bottleneck and flight risk.

> If you can fit the entire system in your head, it's probably a relatively simple codebase.

Or it has good boundaries and I never have the need to load the whole system in my head.

You're not loading the whole OS kernel in your head every time you call fopen(), do you?

> Photoshop file format parser

Would you say that PSD format is an example of good design? Is complexity inherent to the problem domain, or is it accidental?

You are forced to replicate complexity created by other engineers. Woe is you.

My bet is that Adobe also has a lot of unit tests, and contrary to what unit-testing advocates claim, it resulted in a terrible design you are dealing with.

My friend, half of software engineering is handling complexity created by other developers. If you're implementing a Mastodon client, you don't get to just refuse to deal with OAuth because its design offends you on a philosophical level.

But I get to refuse to turn OAuth into a cross-cutting concern in my application. You won't see refresh tokens referenced in the UI code. And I get to use a 3rd-party library that solves 90% of the pain for me.

I strongly disagree on the ratio. If you're building Mastodon client, most of your effort should be spent on features and UX, not on OAuth and the like. If half of your time is spent on those, either you're at the beginning of the project, or you're at the beginning of your career. Or maybe you just care about engineering itself more than the end product.

If you peek at that third party OAuth library, you will discover… it's complex. This is what I mean about pushing the complexity around on your plate. You can make it someone else's problem (and become dependent on them), but the complexity is still there. There is a minimum level of complexity that any OAuth system needs to have in order to function. QED

OAuth library is a perfect example of lousy engineers inventing complexity.

Here's a talk where Jack Diederich mentions it: https://youtu.be/o9pEzgHorH0?t=870

It is indeed complex: 200+ classes. Plenty of unit tests and mocks.

And then there's his implementation:

- 0% unit test coverage.

- Lightweight at less than 200 lines, including blanks and docstrings.

QED.