sabahattink Systematic debugging
Use when: a test fails, a user reports a bug, or behaviour diverges from expectation.
Protocol
- Observe — write down what happens vs what should happen. One sentence each.
- Reproduce — find the smallest input that triggers the bug. If you can't reproduce it, you can't fix it.
- Hypothesize — name one specific cause and one prediction the bug makes if that cause is right.
- Test — prove or disprove the hypothesis with a change that takes less than five minutes.
- If wrong — hypothesize again with what you learned. Don't skip this step.
Rules
- One hypothesis at a time.
- Don't read the whole codebase. Start at the symptom and walk outward.
- Reproduction is the commit-worthy artefact: capture it as a failing test before you fix anything.
- When stuck, tell the rubber duck the last three things you ruled out. The answer is usually in what you haven't ruled out.
Anti-patterns
- Changing five things at once and hoping one fixed it.
- Reading error messages as noise. Read them as constraints.
- Blaming the framework before proving the bug isn't yours.