Unit testing is "what" you test, it's your scope. And regression testing is "why" you're testing, you running tests to detect regressions.

Right, but if you're testing the 'why' and calling it a unit test... confusion ensues...

Is it that confusing that units of code are subject to change, hence subject to regressions, hence their tests are used to prevent regression?

1. Unit testing is a kind of functional testing. On a unit.

2. And regression testing is rerunning your existing functional tests after, say, refactoring, to see if they pass.

Complex? Confusing? Which part of this precisely is confusing?

Realisticly the problem here is;

The headline says they're generating unit tests automatically.

Which means I expect that I run a command, and it plops out unit test code. automatically. without my interaction.

The article is about recording repl interactions. that's not automatic.

and really, they look like implementation details? so bad examples? I don't know scheme, so shrug

Your problem appears to be your entire focus is pointlessly nitpicking the meaning of everyone’s words where enough context exists to trivially disambiguate it.

You gotta pick a better hobby.

You said a unit test is 'what' you test?

So if I say 'I wrote a unit test' what kind of test do you expect?

I expect test for a unit. Honestly don’t know what your problem is.