Investigate a reported problem, find its root cause, and create a GitHub issue with a TDD fix plan. This is a mostly hands-off workflow - minimize questions to the user.
Process
1. Capture the problem
Get a brief description of the issue from the user. If they haven't provided one, ask ONE question: "What's the problem you're seeing?"
Do NOT ask follow-up questions yet. Start investigating immediately.
2. Explore and diagnose
Use the Agent tool with subagent_type=Explore to deeply investigate the codebase. Your goal is to find:
- Where the bug manifests (entry points, UI, API responses)
- What code path is involved (trace the flow)
- Why it fails (the root cause, not just the symptom)
- What related code exists (similar patterns, tests, adjacent modules)
Look at:
- Related source files and their dependencies
- Existing tests (what's tested, what's missing)
- Recent changes to affected files (
git logon relevant files) - Error handling in the code path
- Similar patterns elsewhere in the codebase that work correctly
3. Identify the fix approach
Based on your investigation, determine:
- The minimal change needed to fix the root cause
- Which modules/interfaces are affected
- What behaviors need to be verified via tests
- Whether this is a regression, missing feature, or design flaw
4. Design TDD fix plan
Create a concrete, ordered list of RED-GREEN cycles. Each cycle is one vertical slice:
- RED: Describe a specific test that captures the broken/missing behavior
- GREEN: Describe the minimal code change to make that test pass
Rules:
- Tests verify behavior through public interfaces, not implementation details
- One test at a time, vertical slices (NOT all tests first, then all code)
- Each test should survive internal refactors
- Include a final refactor step if needed
- Durability: Only suggest fixes that would survive radical codebase changes. Describe behaviors and contracts, not internal structure. Tests assert on observable outcomes (API responses, UI state, user-visible effects), not internal state. A good suggestion reads like a spec; a bad one reads like a diff.
5. Create the GitHub issue
Create a GitHub issue using gh issue create with the template below. Do NOT ask the user to review before creating - just create it and share the URL.
Problem
A clear description of the bug or issue, including:
- What happens (actual behavior)
- What should happen (expected behavior)
- How to reproduce (if applicable)
Root Cause Analysis
Describe what you found during investigation:
- The code path involved
- Why the current code fails
- Any contributing factors
Do NOT include specific file paths, line numbers, or implementation details that couple to current code layout. Describe modules, behaviors, and contracts instead. The issue should remain useful even after major refactors.
TDD Fix Plan
A numbered list of RED-GREEN cycles:
-
RED: Write a test that [describes expected behavior] GREEN: [Minimal change to make it pass]
-
RED: Write a test that [describes next behavior] GREEN: [Minimal change to make it pass]
...
REFACTOR: [Any cleanup needed after all tests pass]
Acceptance Criteria
- Criterion 1
- Criterion 2
- All new tests pass
- Existing tests still pass
After creating the issue, print the issue URL and a one-line summary of the root cause.
Mirrored from https://github.com/mattpocock/skills — original author: mattpocock, license: MIT. This is an unclaimed mirror. Content and ownership transfer to the author when they claim this account.