I'm currently discovering (and fixing) non-trivial bugs in obscure edge cases using property-based tests — once that's done, I'll be *very* confident it'll be working as intended. Fun!
Extra important because this is access-related code, i.e. at risk of privilege escalation.
Can highly recommend fast-check for writing property-based tests in JavaScript: https://dubzzz.github.io/fast-check.github.com/
For me, programming is acknowledging I make lots of mistakes, and putting up a lot of guardrails for me to bump into.