Vitest Coverage Planning Capability Pack Skill

Knowledge Freshness

This capability pack is pinned to Vitest 4.1.8, source tag v4.1.8, npm metadata, and coverage documentation verified on 2026-06-03. The reviewed package metadata requires Node ^20.0.0, ^22.0.0, or >=24.0.0.

Retrieval Sources

• https://vitest.dev/guide/coverage.html
• https://vitest.dev/config/coverage.html
• https://vitest.dev/guide/reporters.html
• https://vitest.dev/guide/cli.html
• https://github.com/vitest-dev/vitest/releases/tag/v4.1.8
• https://registry.npmjs.org/vitest/4.1.8
• https://raw.githubusercontent.com/vitest-dev/vitest/v4.1.8/packages/vitest/package.json
• https://raw.githubusercontent.com/vitest-dev/vitest/v4.1.8/docs/guide/coverage.md
• https://raw.githubusercontent.com/vitest-dev/vitest/v4.1.8/docs/config/coverage.md
• https://raw.githubusercontent.com/vitest-dev/vitest/v4.1.8/docs/guide/cli.md

Prefer current Vitest docs, npm metadata, and pinned source files over model memory for provider behavior, coverage options, thresholds, reporters, and CLI behavior.

Scope Note

This is not a generic TDD rule pack, a stop-hook coverage report, or a test-suite generation command. Use it for human-in-the-loop planning of Vitest coverage scope, provider choice, gap triage, threshold policy, changed-file reports, and release gates.

Core Workflow

1. Confirm Vitest version, Node runtime, package manager, coverage provider package, source tag, and coverage command used for review.
2. Inventory test configuration: vitest.config, Vite config, test.coverage, scripts, reporters, output files, and CI command.
3. Choose or validate provider strategy. Use V8 when fast runtime collection fits the environment; consider Istanbul when instrumentation scope or non-V8 runtime constraints matter.
4. Review coverage scope: coverage.include, coverage.exclude, uncovered-file inclusion, generated files, test files, fixtures, and package boundaries.
5. Review report settings: reportsDirectory, reporter list, LCOV/JSON/HTML/JUnit needs, reportOnFailure, and whether the report format supports the reviewer workflow.
6. Review thresholds: lines, functions, branches, statements, per-file behavior, negative uncovered-item limits, and any auto-update policy.
7. Triage gaps by product risk rather than percentage alone: core flows, error paths, adapters, edge cases, state transitions, and recent change areas.
8. Build a coverage plan: tests to add, tests to refactor, low-value files to exclude with rationale, thresholds to ratchet, and checks to run before merge.
9. Produce a recommendation with blockers, safe follow-ups, threshold proposal, validation commands, and owner decisions.

Capability Scope

• Vitest package/source verification
• Coverage provider selection
• Coverage include/exclude review
• Threshold and per-file policy review
• Reporter and artifact planning
• Changed-file coverage triage
• Coverage gap prioritization
• Evidence-based merge or follow-up recommendation

Compatibility

Native

• Claude Code / Claude: use as a reusable Agent Skill for Vitest coverage planning and test-gap review.
• Codex/OpenAI workflows: use as SKILL.md-style instructions for coverage review and release-gate planning.

Manual Adaptation

• Windsurf and Gemini: adapt the workflow and output contract into their skill formats.
• Cursor and Generic AGENTS files: convert the production rules and validation checklist into repository-level test coverage guidance.

Required Inputs

• Vitest version and coverage provider package
• Test command and package manager
• vitest.config or Vite config
• Current coverage output or changed-file context
• Project risk areas and release policy
• Owner expectations for thresholds, exclusions, and follow-up work

Production Rules

• Do not judge test adequacy by aggregate percentage alone; connect gaps to product risk and recent changes.
• Do not add broad exclusions without a written reason and owner agreement.
• Treat threshold decreases, auto-update changes, and per-file policy changes as release-impacting until reviewed.
• Include uncovered source files intentionally; otherwise untouched files can disappear from the report.
• Keep generated code, fixtures, and test helpers out of coverage only when the exclusion is deliberate.
• Prefer small, risk-based threshold ratchets over unrealistic all-at-once coverage targets.
• Keep coverage planning separate from test execution success; passing tests can still leave critical branches uncovered.

Output Contract

1. Source evidence: Vitest version, source tag, npm metadata, coverage docs, and config files reviewed.
2. Configuration inventory: provider, include/exclude, reporters, reports directory, thresholds, and CI command.
3. Gap analysis: uncovered file groups, branches, functions, changed files, and risk areas.
4. Coverage plan: test additions, refactors, exclusions, threshold ratchets, and owner follow-up.
5. Validation plan: exact coverage command, focused test command, report artifact, and CI gate.
6. Recommendation: merge, hold, request changes, or accept with tracked follow-up.

Troubleshooting

Issue: Coverage report ignores untouched source files

Fix: Configure coverage.include with source globs so uncovered files are present in the report.

Issue: V8 coverage is unexpectedly slow

Fix: Check module count and runtime environment. Compare V8 with Istanbul when instrumentation can limit the measured file set.

Issue: Thresholds fail on unrelated files

Fix: Separate global and per-file thresholds, check changed-file scope, and decide whether the failure reflects product risk or stale baseline policy.

Issue: Report artifacts are too noisy for review

Fix: Use targeted reporters such as text-summary, LCOV, JSON, or JUnit depending on whether reviewers need quick triage, CI annotations, or trend ingestion.

Issue: Coverage improves but misses important behavior

Fix: Review branch and function coverage for core workflows, error paths, adapters, and state transitions instead of relying only on line coverage.

Validation Checklist

• Vitest version, source tag, npm metadata, and coverage docs verified.
• Node runtime requirement checked.
• Coverage provider selected and provider package identified.
• Include/exclude scope reviewed.
• Reports directory and reporter list checked.
• Thresholds reviewed for global, per-file, and uncovered-item behavior.
• Changed-file and product-risk gaps triaged.
• Exclusions documented with rationale.
• Validation commands and artifacts recorded.
• Merge, hold, request-changes, or follow-up recommendation documented.

• Source repositorygithub.com 2026-06-03
• Documentationvitest.dev
• Package downloadgithub.com
• Submitted by oktofeesh12026-06-03