Test

DLC: Test Coverage Analysis

Run the test suite, measure coverage, and create a GitHub issue for failures and coverage gaps.

Before running, read [../dlc/references/ISSUE-TEMPLATE.md](../dlc/references/ISSUE-TEMPLATE.md) now for the issue format, and read [../dlc/references/REPORT-FORMAT.md](../dlc/references/REPORT-FORMAT.md) now for the findings data structure.

Step 1: Detect Test Framework

Scan for test configuration:

| Config / Pattern | Framework | Coverage Tool | |-----------------|-----------|---------------| | vitest.config.* / vite.config.* (with test) | Vitest | @vitest/coverage-v8 | | jest.config.* / package.json (with jest) | Jest | Built-in (--coverage) | | pytest.ini / pyproject.toml (with pytest) / conftest.py | pytest | pytest-cov | | Cargo.toml + tests/ dir | cargo test | cargo-tarpaulin or cargo-llvm-cov | | go.mod + *_test.go files | go test | Built-in (-cover) | | .rspec / Gemfile (with rspec) | RSpec | simplecov |

Also detect test runner scripts in package.json or the project's task runner.

Step 2: Run Test Suite with Coverage

Execute tests with coverage enabled:

Select the tool based on availability (command -v) and detected framework, not exit codes — test runners exit non-zero when tests fail, which is a valid result to capture.

# Node.js (Vitest) — if vitest config detected
npx vitest run --coverage --reporter=json 2>/dev/null

# Node.js (Jest) — if jest config detected
npx jest --coverage --json 2>/dev/null

# Python
command -v pytest >/dev/null 2>&1 && pytest --cov=. --cov-report=json --tb=short 2>/dev/null

# Rust — select coverage tool by availability
if command -v cargo-tarpaulin >/dev/null 2>&1; then
  cargo tarpaulin --out json 2>/dev/null
elif command -v cargo-llvm-cov >/dev/null 2>&1; then
  cargo llvm-cov --json 2>/dev/null
fi

# Go
go test -cover -coverprofile=coverage.out -json ./... 2>/dev/null

# Custom test script — select runner by availability
if command -v bun >/dev/null 2>&1; then
  bun test 2>/dev/null
elif command -v npm >/dev/null 2>&1; then
  npm test 2>/dev/null
fi

Capture both:

• Test results: pass/fail status per test, failure messages
• Coverage metrics: line coverage %, branch coverage %, per-file breakdown

Step 3: Identify Coverage Gaps in Recent Changes

Focus on files changed recently (not just overall coverage):

# Files changed in last 5 commits
git diff --name-only HEAD~5..HEAD -- '*.ts' '*.js' '*.py' '*.go' '*.rs'

# Files changed vs main branch
git diff --name-only origin/main...HEAD

For each changed file:

1. Check if a corresponding test file exists
2. Check coverage percentage for that specific file
3. Flag files with | tail -1

git log $MB..HEAD --format="%H %ct" --diff-filter=A -- | tail -1

**Scope**: Only check files **added on the current branch** (the `$MB..HEAD` range above). Files that already exist in `main` are excluded — the TDD order signal is only meaningful for new files introduced in this branch. Reuse the same file list from `git diff --name-only $MB..HEAD`.

For each pair, first compare **commit hashes**, then timestamps:

| Condition | Action |
|-----------|--------|
| Either file has no `--diff-filter=A` output (shallow clone, renamed/moved file, or file not added on this branch) | Skip pair — log a note to stdout (not a finding): "Skipping TDD order check for `{file}`: insufficient git history" |
| Both files share the same add-commit hash | No per-pair finding — same-commit pair counts as TDD-confirming for the branch-level check |
| Add-commit hashes differ but timestamps are equal | Skip pair — log a note to stdout (not a finding): "Skipping TDD order check for `{source}` / `{test}`: unable to determine order (identical-second commit timestamps)" |
| Source add-commit timestamp < test add-commit timestamp | **Low** `tdd-order` finding — test written after source (confirmation bias risk) |
| Test add-commit timestamp < source add-commit timestamp | No finding — TDD discipline confirmed for this pair |

If at least one new source/test pair was evaluated, **no** new source file in the branch diff is missing a corresponding test file, and **all** evaluated pairs have pre-dating or same-commit tests, emit a single **Info** `tdd-order` finding: "TDD discipline confirmed for this branch."

**Finding messages**:

| Severity | Type | Message |
|----------|------|---------|
| **Low** | `tdd-order` | "Test for `{source}` written after source — risk of confirmation bias in test assertions" |
| **Info** | `tdd-order` | "TDD discipline confirmed for this branch" |

## Step 4: Classify Findings

Map results to the findings format from REPORT-FORMAT.md.

**Severity mapping** (reinforced here for defense-in-depth):

| Finding Type | Severity |
|-------------|----------|
| Test suite fails to run (config error, missing deps) | **Critical** |
| Failing tests (regressions) | **High** |
| Changed files with 0% coverage | **High** |
| Overall coverage below project threshold | **Medium** |
| Changed files with < 80% coverage | **Medium** |
| Missing test file for new module | **Medium** |
| Flaky tests (pass on retry) | **Low** |
| Source file committed before its test file | **Low** |
| Coverage informational metrics | **Info** |
| TDD discipline confirmed (all tests pre-date source or are added in the same commit) | **Info** |

## Step 5: Create GitHub Issue

**Read [../dlc/references/ISSUE-TEMPLATE.md](../dlc/references/ISSUE-TEMPLATE.md) now** and format the issue body exactly as specified.

**Critical format rules** (reinforced here):
- Title: `[DLC] Testing: {summary — e.g. "3 failures, 72% coverage"}`
- Label: `dlc-test`
- Body must contain: Scan Metadata table, Findings Summary table (severity x count), Findings Detail grouped by severity, Recommended Actions, Raw Output in collapsed details
- Include a **Coverage Summary** subsection in the metadata:

```markdown
### Coverage Summary

| Metric | Value | Target |
|--------|-------|--------|
| Line Coverage | {n}% | 80% |
| Branch Coverage | {n}% | 70% |
| Files with 0% | {n} | 0 |

REPO=$(gh repo view --json nameWithOwner -q .nameWithOwner)
BRANCH=$(git branch --show-current)
TIMESTAMP=$(date +%s)
BODY_FILE="/tmp/dlc-issue-${TIMESTAMP}.md"

gh issue create \
  --repo "$REPO" \
  --title "[DLC] Testing: {summary}" \
  --body-file "$BODY_FILE" \
  --label "dlc-test"

If issue creation fails, save draft to /tmp/dlc-draft-${TIMESTAMP}.md and print the path.

Step 6: Report

Test analysis complete.
  - Framework: {detected framework}
  - Tests: {passed} passed, {failed} failed, {skipped} skipped
  - Coverage: {line}% line, {branch}% branch
  - Changed files coverage: {n}/{total} above threshold
  - Issue: #{number} ({url})

If all tests pass and coverage is above threshold, skip issue creation and report: "All tests passing. Coverage meets threshold ({n}%)."

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: rube-de
• Source: rube-de/cc-skills
• License: MIT

Install and usage instructions live in the source repository linked above.