This is a bit disingenuous, don't you think? There's technically a spectrum from low-level to high-level code, but in practice it's not too difficult to set a limit on how far down the stack you're willing to go while building. Writing a new testing framework is qualitatively different from writing a new OS or filesystem, and you know it just as well as everyone else does.

I was trying to make a point... Apparently not very well ;)

But let's take on the testing framework question. When I work in Go or in Python I use the testing frameworks that are part of that ecosystem. When I worked with C++ I'd use the Boost testing framework. Or Google's open source testing framework. Engineers I work with that do front-end development use Playwright (and I'm sure some other existing framework for unit tests).

Can't you do your own thing? sure. You'd be solving a lot of problems that other people have already solved. Over time the thing you did on your own will require more work. You need to weigh all of that vs. using something off the shelf. 9 times out of 10, most people, should use tooling that exists and focus on the actual product they want to build.

That said I work for a large company where we build a lot of additional in-house tooling. It makes sense because: a) it's a specialized domain - there's nothing off the shelf that addresses our specific needs. b) we are very large and so building custom tools is an investment that can be justified over the entire engineering team. We still use a ton of stuff off the shelf.

I don't see what the parent was saying. I think most of the time people choose to use existing bits for good reasons. When I started my career you pretty much had to do most stuff yourself. These days you almost always can find a good off the shelf option for most "standard" things you're trying to do. If you want to write your own testing framework for fun, go for it. If you're trying to get something else done (for business or other reasons) it's not something that usually makes sense. That said it's not like we have a shortage of people trying to do new things or revisit old things, for fun or profit. We have more than ever (simply because we have more than ever people doing software in general).