Recently asked Claude Code how to do more thorough tests and described how I imagine it and it set up Hypothesis and mutmut testing. The latter is quite cool, it introduces bugs in the code like swapping values and relational operators and checks if any test catches the bug. If not, your tests are probably not thorough enough. Better than just line coverage checks.
Fuzzing as a concept is heavily underused in routine testing. People will usually focus on positive flows and some obvious/typical negative ones. But it's almost impossible to have the time to write exhaustive testing to cover all negative and boundary scenarios. But the good news is, you don't actually have to. There are so many tools now that can almost exhaustively generate tests for you at all levels. The bad news, they are not so widely used.
Using the phrase "without the benefit of hindsight" is interesting. The hardest thing with any technology is knowing when to spend the effort/money on applying it. The real question is: do you want to spend your innovation tokens on things like this? If so, how many? And where?
Not knocking this, just saying that it is easy to claim improvements if you know there are improvements to be had.
Not knocking this, just saying that it is easy to claim improvements if you know there are improvements to be had.