Ask HN: How do you find a bug in a software?

I'm a happy Sentry user, https://sentry.io

Run tests on each of the micro services and if they are all ok, test the next level and etc.

That might be the downside of micro services : if all of them works well, but orchestrating them generates new bugs. Hard to find where it crashes.

Bugs themselves are usually found QA, customers, logs, and/or metrics.

To find where to fix it, logs, crash dumps (another kind of log), and/or isolation (going "down" the stack and checking along the way).

Rarely find bugs via unit tests, apart from in complex logic

true; unit tests will rarely find bugs, especially if you're writing the tests after the code.

Unit tests are meant to ensure that when you add features, fix bugs, or refactor, that you don't break what's already working.

If this means your unit tests don't catch bugs, then it could be that you're not introducing any! yay!

But I have found that by forcing myself into TDD, I do find more cases than when I was writing tests after code.

By writing the tests before I've begun the implementation, it forces you to think about preconditions, invariants, and postconditions in a more disciplined way.

Watch your logs ?