bugfix-without-test#

Fixing a bug without a test means (a) you don't know the fix actually works, and (b) there's nothing to stop the bug from coming back next refactor. A fix without a regression test is provisional at best.

Symptoms#

• Diff contains code changes but no test changes.
• Existing tests still pass, but none of them would have failed under the original bug.
• PR description describes a bug scenario that no test exercises.
• The fix is a one-liner and no one will remember why it exists six months later.

What to do#

• Reproduce the bug as a failing test first. Run it. Confirm it fails for the right reason.
• Apply the fix. Run the test again. Confirm it passes.
• Keep the test in the suite. It becomes the regression guard.
• If the bug is hard to test (timing, environment, flaky), say so explicitly and describe what manual verification was done. Don't silently skip.
• For bugs discovered in production, add the test at the lowest level that reproduces the issue — unit if possible, integration if not.