geometry-tower-defense/.omc/skills/regression-suite/SKILL.md

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---
name: regression-suite
description: "Map test coverage to GDD critical paths, identify fixed bugs without regression tests, flag coverage drift from new features, and maintain tests/regression-suite.md. Run after implementing a bug fix or before a release gate."
argument-hint: "[update | audit | report]"
user-invocable: true
allowed-tools: Read, Glob, Grep, Write, Edit
---
# Regression Suite
This skill ensures that every bug fix is backed by a test that would have
caught the original bug — and that the regression suite stays current as the
game evolves. It also detects when new features have been added without
corresponding regression coverage.
A regression suite is not a new test category — it is a **curated list of
tests already in `tests/`** that collectively cover the game's critical paths
and known failure points. This skill maintains that list.
**Output:** `tests/regression-suite.md`
**When to run:**
- After fixing a bug (confirm a regression test was written or identify gap)
- Before a release gate (`/gate-check polish` requires regression suite exists)
- As part of sprint close to detect coverage drift
---
## 1. Parse Arguments
**Modes:**
- `/regression-suite update` — scan new bug fixes this sprint and check
for regression test presence; add new tests to the suite manifest
- `/regression-suite audit` — full audit of all GDD critical paths vs.
existing test coverage; flag paths with no regression test
- `/regression-suite report` — read-only status report (no writes); suitable
for sprint reviews
- No argument — run `update` if a sprint is active, else `audit`
---
## 2. Load Context
### Step 2a — Load existing regression suite
Read `tests/regression-suite.md` if it exists. Extract:
- Total registered regression tests
- Last updated date
- Any tests flagged as `STALE` or `QUARANTINED`
If it does not exist: note "No regression suite found — will create one."
### Step 2b — Load test inventory
Glob all test files:
```
tests/unit/**/*_test.*
tests/integration/**/*_test.*
tests/regression/**/*
```
For each file, note the system (from directory path) and file name.
Do not read test file contents unless needed for name-to-test mapping.
### Step 2c — Load GDD critical paths
For `audit` mode: read `design/gdd/systems-index.md` to get all systems.
For each MVP-tier system, read its GDD and extract:
- Acceptance Criteria (these define the critical paths)
- Formulas section (formulas must have regression tests)
- Edge Cases section (known edge cases should have regression tests)
For `update` mode: skip full GDD scan. Instead read the current sprint plan
and story files to find stories with Status: Complete this sprint.
### Step 2d — Load closed bugs
Glob `production/qa/bugs/*.md` and filter for bugs with a `Status: Closed`
or `Status: Fixed` field. Note:
- Which story or system the bug was in
- Whether a regression test was mentioned in the fix description
---
## 3. Map Coverage — Critical Paths
For `audit` mode only:
For each GDD acceptance criterion, determine whether a test exists:
1. Grep `tests/unit/[system]/` and `tests/integration/[system]/` for file names
and function names related to the criterion's key noun/verb
2. Assign coverage:
| Status | Meaning |
|--------|---------|
| **COVERED** | A test file exists that targets this criterion's logic |
| **PARTIAL** | A test exists but doesn't cover all cases (e.g. happy path only) |
| **MISSING** | No test found for this critical path |
| **EXEMPT** | Visual/Feel or UI criterion — not automatable by design |
3. Elevate MISSING items that correspond to formulas or state machines to
**HIGH PRIORITY** gap — these are the most likely regression sources.
---
## 4. Map Coverage — Fixed Bugs
For each closed bug:
1. Extract the system slug from the bug's metadata
2. Grep `tests/unit/[system]/` and `tests/integration/[system]/` for a test
that references the bug ID or the specific failure scenario
3. Assign:
- **HAS REGRESSION TEST** — a test was found that would catch this bug
- **MISSING REGRESSION TEST** — bug was fixed but no test guards against recurrence
For MISSING REGRESSION TEST items:
- Flag them as regression gaps
- Suggest the test file path: `tests/unit/[system]/[bug-slug]_regression_test.[ext]`
- Note: "Without this test, this bug can silently return in a future sprint."
---
## 5. Detect Coverage Drift
Coverage drift occurs when the game grows but the regression suite doesn't.
Check for drift indicators:
- Stories completed this sprint with no corresponding test files in `tests/`
- New systems added to `systems-index.md` since the last regression-suite update
- GDD sections added or revised since the regression suite was last updated
(use Grep on GDD file modification hints if available, or ask the user)
- `tests/regression-suite.md` last-updated date vs. current date — if gap >
2 sprints, flag as likely stale
---
## 6. Generate Report and Suite Manifest
### Report format (in conversation)
```
## Regression Suite Status
**Mode**: [update | audit | report]
**Existing registered tests**: [N]
**Test files scanned**: [N]
### Critical Path Coverage (audit mode only)
| System | Total ACs | Covered | Partial | Missing | Exempt |
|--------|-----------|---------|---------|---------|--------|
| [name] | [N] | [N] | [N] | [N] | [N] |
**Coverage rate (non-exempt)**: [N]%
### Bug Regression Coverage
| Bug ID | System | Severity | Has Regression Test? |
|--------|--------|----------|----------------------|
| BUG-NNN | [system] | S[N] | YES / NO ⚠ |
**Bugs without regression tests**: [N]
### Coverage Drift Indicators
[List new systems or stories with no test coverage, or "None detected."]
### Recommended New Regression Tests
| Priority | System | Suggested Test File | Covers |
|----------|--------|---------------------|--------|
| HIGH | [system] | `tests/unit/[system]/[slug]_regression_test.[ext]` | BUG-NNN / AC-[N] |
| MEDIUM | [system] | `tests/unit/[system]/[slug]_test.[ext]` | [criterion] |
```
### Suite manifest format (`tests/regression-suite.md`)
The manifest is a curated index — not the tests themselves, but a registry
of which tests should always pass before a release:
```markdown
# Regression Suite Manifest
> Last Updated: [date]
> Total registered tests: [N]
> Coverage: [N]% of GDD critical paths
## How to run
[Engine-specific command to run all regression tests]
## Registered Regression Tests
### [System Name]
| Test File | Test Function (if known) | Covers | Added |
|-----------|--------------------------|--------|-------|
| `tests/unit/[system]/[file]_test.[ext]` | `test_[scenario]` | AC-N / BUG-NNN | [date] |
## Known Gaps
Tests that should exist but don't yet:
| Priority | System | Suggested Path | Covers | Reason Not Yet Written |
|----------|--------|----------------|--------|------------------------|
| HIGH | [system] | `tests/unit/[system]/[path]` | BUG-NNN | Bug fixed without test |
## Quarantined Tests
Tests that are flaky or disabled (do not run in CI):
| Test File | Function | Reason | Quarantined Since |
|-----------|----------|--------|-------------------|
| (none) | | | |
```
---
## 7. Write Output
Ask: "May I write/update `tests/regression-suite.md` with the current
regression suite manifest?"
For `update` mode: append new entries; never remove existing entries
(use `Edit` with targeted insertions).
For `audit` mode: rewrite the full manifest with updated coverage data.
For `report` mode: do not write anything.
After writing (if approved):
- For each HIGH priority gap: "Consider creating the missing regression test
before the next sprint. Run `/test-helpers` to scaffold the test file."
- If bug regression gaps > 0: "These bugs can silently return without regression
tests. The next sprint should include a story to write the missing tests."
- If coverage drift detected: "Regression suite may be drifting. Consider
running `/regression-suite audit` at the next sprint boundary."
Verdict: **COMPLETE** — regression suite updated. (If user declined write: Verdict: **BLOCKED**.)
---
## Collaborative Protocol
- **Never remove existing regression tests from the manifest** without
explicit user approval — removing a test that was deliberately written is a
regression risk itself
- **Gaps are advisory, not blocking** — surface them clearly but do not prevent
other work from proceeding (except at release gate where regression suite is required)
- **Quarantine is not deletion** — tests with intermittent failures should be
quarantined (noted in manifest) but not removed; they should be fixed by
`/test-flakiness`
- **Ask before writing** — always confirm before creating or updating the manifest