dennisonbertram Regression Guard
Post-fix test-debt payoff loop. Takes the git diff of a recent fix as input and generates targeted tests to prevent the bug from returning.
Usage
/regression-guard [commit-range]
If no commit range is specified, uses HEAD~3..HEAD.
Step 1 — Review What Was Fixed
Build a structured summary from git:
git log --oneline -10
git diff HEAD~3..HEAD
git log -1 --format=%B
Produce:
- What broke — the failure mode
- What changed — specific code paths
- Files and functions touched
- Issue/PR reference
Step 2 — Generate Unit Tests
Write the smallest set of unit tests that lock in the correct behavior:
tests/unit/<area>/<fix-slug>.test.<ext>
Rules:
- Each test must be red when reverted against the pre-fix state
- Cover the happy path AND the corrected edge cases
- State which assertion would be red if reverted
Step 3 — Generate Regression Tests
Write regression tests that construct the exact pre-fix state:
tests/regression/<area>/<fix-slug>-regression.test.<ext>
Rules:
- Include a top-of-file comment identifying the pre-fix state and symptom
- The test must pass the full check suite with no manual edits
Step 4 — Audit: Could This Have Been Caught Earlier?
Answer honestly. Pick the most relevant gap category:
- Missing boundary test — contract assertion at a module seam
- Missing negative test — error path never exercised
- Non-hermetic test harness — shared state leaked between tests
- Missing integration coverage — only reproduced under production shape
- Contract drift — upstream contract widened/narrowed without downstream rebase
For each gap, write a concrete, actionable suggestion. No generic "add more tests."
Step 5 — Recommend Integration Testing Additions
Name:
- The specific test command to extend
- The specific file to add a test into (or create)
- A concrete test stub that would have caught the bug
Output Report
Write to docs/investigations/<date>-regression-guard-<fix-slug>.md:
- Fix summary
- Generated unit tests (file paths + descriptions)
- Generated regression tests (file paths + pre-fix state each reconstructs)
- "Could this have been caught earlier?" diagnosis
- Integration testing recommendations
- Baseline comparison table
Ship as a Draft PR
- Create a new branch
- Commit the generated test files and output report
- Open a draft PR against main
- Never push directly to main