Skill: aptratcn/xiaobai-systematic-debugging (version 2.0.0)

--- name: systematic-debugging version: 2.0.0 description: 4-phase root cause debugging. Never guess, find the cause. Based on real production debugging methodology. Trigger on: 'bug', 'error', 'not working', 'broken', 'debug', 'fix this'. emoji: 🔍 --- # Systematic Debugging 🔍 4 phases. No guessing. Find root cause. ## The 4 Phases ``` Phase 1: OBSERVE → What exactly is wrong? (Gather evidence) Phase 2: ISOLATE → Where does it go wrong? (Narrow scope) Phase 3: HYPOTHESIZE → Why does it go wrong? (Form theory) Phase 4: VERIFY → Is it actually fixed? (Prove it) ``` ## Phase 1: OBSERVE (Don't Skip This) **Before touching any code, answer these:** ``` □ What is the expected behavior? □ What is the actual behavior? □ When did it start? (What changed?) □ Is it reproducible? (100%? Intermittent?) □ What's the exact error message / log output? □ What environment? (OS, version, dependencies) ``` **Common mistake:** Jumping to "I think it's because..." without observing first. **What to do:** - Read the actual error (copy-paste, don't paraphrase) - Check logs (recent ones first) - Reproduce the issue (if possible) - Document what you see ## Phase 2: ISOLATE (Narrow the Scope) **Binary search for the bug:** ``` 1. Is the problem in my code or external? → Comment out my code. Still broken? External. 2. Is it in the input, processing, or output? → Print/log at each stage. 3. Is it in one specific file/function? → Remove files/functions one by one. → Bug disappears? That's where it is. 4. Is it a specific condition? → Test with different inputs. → Pattern emerges? Root cause narrows. ``` **Techniques:** - `git bisect` — Find the commit that introduced the bug - Print statements at boundaries - Comment out code sections - Test with minimal reproduction ## Phase 3: HYPOTHESIZE (Form a Theory) **Write your hypothesis BEFORE fixing:** ``` I believe [X] is broken because [Y]. Evidence supporting: - [Observation 1] - [Observation 2] Evidence against: - [Observation 3] If I change [Z], the fix should: - Make [test case] pass - Not break [other thing] ``` **Common mistake:** Fixing without understanding. You might "fix" the symptom, not the cause. **Anti-patterns:** - ❌ "Let me try changing this..." (random fixing) - ❌ "This usually works..." (cargo cult debugging) - ❌ "It's probably a race condition" (vague guess) ## Phase 4: VERIFY (Prove It) **Before claiming "fixed":** ``` □ Original test case now passes □ Edge cases tested □ No new regressions introduced □ Error no longer appears in logs □ Fix makes sense given the hypothesis ``` **Verification checklist:** ```bash # Run the failing test npm test -- --grep "failing test" # Check logs for errors tail -f /var/log/app.log # Test edge cases [try empty input, huge input, unicode, etc.] # Run full test suite npm test ``` ## Real Example **Bug:** "User login sometimes fails" ``` Phase 1 OBSERVE: - Error: "Invalid token" (not "wrong password") - Intermittent (10% of logins) - Started after deploying auth-service v2.3 - Only on mobile, not desktop Phase 2 ISOLATE: - Network logs: token arrives intact - Auth service: token validation fails intermittently - Added logging: token format varies slightly Phase 3 HYPOTHESIZE: - Mobile client generates tokens with different encoding - v2.3 tightened token validation - Theory: mobile token format doesn't match new validation Phase 4 VERIFY: - Fixed token format in mobile client - Tested 100 logins on mobile: 100% success - Tested desktop: still works - Checked logs: no "Invalid token" errors ``` ## Trigger Phrases - "bug", "error", "not working" - "broken", "debug", "fix this" - "doesn't work", "fails", "crash" - "调试", "修复", "报错" ## Integration - **EVR Framework** — Each phase is Execute/Verify - **Cognitive Debt Guard** — Document bugs in code review - **Error Recovery** — What to do after finding the cause ## License MIT


Security scan verdicts — ClawScan: clean | static analysis: clean | VirusTotal: clean | SkillSpector: clean (LOW)