>“Finding out that it doesn't” means that you didn’t properly reason through the code beforehand, checking all your assumptions against what the code and underlying systems are actually guaranteeing. This may be a matter of formal education (proving computer science theorems and algorithmic correctness in university), I don’t know.
We're not writing theorems, dude.
Except in the equally pedantic sense that every program is a proof to a theorem...
We're writing plain enterprise and web software, closer to CRUD than NASA.
If you said that even before LLMs 0.1% of teams "checked all assumptions against what the code and underlying systems are actually guaranteeing" in any kind of formal way, you'd be overestimating it.
Who’s “we” here? Formal verification isn’t common, sure. But you don’t speak for all programmers. You might work on “plain enterprise and web software”. But there’s still plenty of other software out there that many of us work on. And lots of code being written for internal use (e.g., data analysis code) that needs to be correct.
Of course, even enterprise and web software benefits from a little rigorous thinking. It’s pretty wild that understanding your code and its assumptions and informally proving it works is controversial. But I guess that explains why most software I use has actively gotten worse over the years.
I’m not talking about formal verification, but about diligent informal or semi-formal reasoning through the code, so that you can rightfully claim that you understand the code and will be unlikely to be surprised by its behavior. Having learned formal verification does train that form of exhaustive reasoning about properties of the program. This practice also has you structure the code such (and select your dependencies such) that you can reason about all relevant properties. This is perfectly applicable to what you’d call CRUD and enterprise applications (that’s half the projects I earn my living with). Testing and fuzzing are complementary, but not a substitute by any stretch.