Finding Bugs

Finding Bugs Sep 19, 2026 Are generative (randomized) tests significantly more effective than example-based unit-tests at discovering bugs? There’s an interesting discussion about this on lobste.rs. One argument in favor of unit tests is, paraphrasing My generic fuzzer wasn’t able to find this tricky bug in Rust regex crate. To me, it seems that generative testing should shake out that particular creature, so I wrote a lil fuzzer of my own, and it indeed discovered another bug in that version of regex, and then the one I was after. I didn’t find anything in the latest version. I like to do a write up about the process, as it is a good case study for how one approaches a problem like this. I want to be extra clear that my argument is very weak here, as I know exactly the bug I am after, and I even know that fuzzers can find it. My primary goal is to teach you the techniques, leaving it to your judgment just how effective they are. That being said, I think finding a second bug validates…