[skipkey]

The one thing I would add is, if at all possible, write a unit test that fails, reproducing the bug. I have found when working on a code base that is only lightly unit tested, it’s one of the best ways to increase coverage.

[Brystephor]

100%. In general, if you're submitting a PR for a bug fix then an automated test (ideally a unit test) should be included in the PR that tests the bug fix.