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Vitest Coverage Planning Capability Pack Skill

Expert Vitest coverage planning skill for choosing providers, scoping reports, setting thresholds, triaging gaps, and designing practical coverage gates.

by oktofeesh1·added 2026-06-03·
Claude CodeCodexWindsurfGeminiCursorCLI
HarnessClaude CodeCodexWindsurfGeminiCursorCLI
Level:expertType:capability-packVerified:validated
Review first — review before installing

Open the source and read safety notes before installing.

Safety notes

  • Installing Vitest and coverage providers adds npm packages to the selected project environment; pin reviewed versions and use project-local installs.
  • Coverage runs execute the project test suite and can use test fixtures, network mocks, databases, or generated artifacts configured by the project.
  • Vitest coverage can clean the configured reports directory before a run; confirm the reports directory is disposable before enabling coverage in shared workflows.
  • Threshold changes can block or unblock CI; review threshold updates separately from test additions.
  • The source ZIP is external and version-pinned for reference; package trust should remain a maintainer decision.

Privacy notes

  • Coverage output can reveal source paths, module names, uncovered function names, branch structure, report file names, and project layout.
  • HTML, JSON, LCOV, and JUnit artifacts can include snippets, line ranges, and package structure from the reviewed project.
  • Keep public review notes focused on aggregate gaps, file groups, risk areas, and validation commands; omit sensitive implementation details that do not need to be public.

Prerequisites

  • JavaScript or TypeScript project using Vitest or evaluating a Vitest coverage gate
  • Test command, package manager, and `vitest.config` or Vite config
  • Current coverage report, changed-file context, or uncovered source inventory
  • Project risk areas, owner expectations, and release policy for test gaps
  • Agreement on whether coverage is advisory, blocking, per-file, or trend-based

Schema details

Install type
package
Reading time
9 min
Troubleshooting
Yes
Source repository stats
Scope
Source repo
Package metadata
Skill and platform metadata
Skill type
capability-pack
Skill level
expert
Verification
validated
Verified at
2026-06-03
Retrieval sources
https://vitest.dev/guide/coverage.htmlhttps://vitest.dev/config/coverage.htmlhttps://vitest.dev/guide/reporters.htmlhttps://vitest.dev/guide/cli.htmlhttps://github.com/vitest-dev/vitest/releases/tag/v4.1.8https://registry.npmjs.org/vitest/4.1.8https://raw.githubusercontent.com/vitest-dev/vitest/v4.1.8/packages/vitest/package.jsonhttps://raw.githubusercontent.com/vitest-dev/vitest/v4.1.8/docs/guide/coverage.mdhttps://raw.githubusercontent.com/vitest-dev/vitest/v4.1.8/docs/config/coverage.mdhttps://raw.githubusercontent.com/vitest-dev/vitest/v4.1.8/docs/guide/cli.md
Tested platforms
ClaudeCodexWindsurfGeminiCursorGeneric AGENTS
PlatformSupportInstall path
claude-codeNative.claude/skills/<skill-name>/SKILL.md
codexNative.agents/skills/<skill-name>/SKILL.md
windsurfNative.windsurf/skills/<skill-name>/SKILL.md
geminiNative.gemini/skills/<skill-name>/SKILL.md or .agents/skills/<skill-name>/SKILL.md
cursorAdapter.cursor/rules/<skill-name>.mdc
cliManualAGENTS.md or tool-specific context file
Full copyable content
# Trigger
"Apply the Vitest coverage planning capability pack to this test coverage gap."

# Required output
1) Vitest package/source version and coverage provider inventory
2) Coverage scope, include/exclude, reporters, and threshold review
3) Coverage gap findings with prioritized test-plan recommendations
4) Validation plan and merge, hold, or follow-up recommendation

About this resource

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

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.
#vitest#test-coverage#coverage-planning#testing#capability-pack

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