[tty2300]

In 2019 you could build a compiler in your free time for free so that probably says something about modern development practicices.

I have been working on my current codebase for almost a year now and still haven't seen half of it. There is no just read over it because its massive. Tests are the only thing that makes it manageable. When I want to change something I can find the part that needs to change but I have no idea what features I don't know about that depend on that feature doing something. Tests allow me to very quickly automatically scan the code base to show what things changed.

[kragen]

Knuth had previously built a couple of compilers in 1957 and 1958, as you can read in the interview I linked, but it's sort of ambiguous as to whether it was "in his free time" — his job gave him and his friends access to a computer but I don't think writing compilers was declared to be part of their responsibilities. It wasn't for free, though. I think what that says about modern development practices is that we have cheap computers.

I agree that tests are very valuable for the reason you describe, as well as for other reasons. What codebase are you working on?