And sometimes you find errors in code that absolutely should never have errors: I found an (as of yet not-root-caused) error in sqlite (no crash or coredump, just returns the wrong data, and only when using sqlite in ram-only-mode). Had to move to postgres for that reason alone. This is part of the reason why I have a strong anti-library bias (and I sound like a lunatic to most colleagues because they "have never had a problem" with $favorite_library -- to which my response is: "how do you _know_?"[0], which often makes me sound like I'm being unreasonably difficult).

Sometimes, only thing you can do is let the plague spread, and hope that the people who survive start showering and washing their hands.

[0]: I once interviewed at a company that sold a kind of on-prem VM hosting and storage product. They were shipping a physical machine with Linux and a custom filesystem (so not ZFS), and they bragged about how their filesystem was very fast, much faster than ZFS or Btrfs on SSDs. I asked them, if they were allowed to tell me how they achieved such consistent numbers. They listed a few things, one of which was: "we disabled block-level check-summing". I asked: "how do you prevent corruption?". They said: "we only enable check-summing during the nightly tests". So, a little unsettled, I asked: "you do not do _any_ check-summing at any point in production"? They replied: "Exactly. It's not necessary". So, throwing caution to the wind (at this point I did not care to get the job), I asked: "And you've never had data corruption in production"? They said: "Never. None". To which I replied: "But how do you _know_"? My no-longer-future-coworker thought for a few seconds, and realization flashed across his face. This was a company that had actual customers on 2 continents, and was pulling in at least millions per year. They were probably silently corrupting customer data, while promising that they were the solution -- a hospital selling snake-oil, while thinking it really is medicine.

Are you talking about user flows and multiple interactions that are happening and data exchange that PBT before that wasn't able to address?

Interesting. What kind of properties are you checking?