Vitest

Vitest Skill

Next generation testing framework powered by Vite.

Ecosystem Graph Preview

graph LR
  vitest["vitest"]:::core
  classDef core fill:#f9f,stroke:#333,stroke-width:4px;
  vitest -- "works well with" --> playwright
  vitest -- "works well with" --> react

Recommended Next Skills

• playwright (Score: 0.85) Why: Direct relationship, Both are Testing, Shared ecosystem (javascript), Logical next step
• react (Score: 0.65) Why: Direct relationship, Shared ecosystem (javascript), Logical next step
• biome (Score: 0.4) Why: Both are Developer Tools, Shared ecosystem (javascript), Can deploy to any

Quick Start

Vitest is a blazing fast unit test framework powered by Vite. It is a drop-in replacement for Jest but significantly faster as it shares the same configuration and transformation pipeline as Vite.

npm install -D vitest

Production Patterns

Setup Files

Instead of importing beforeEach and describe manually in every test file, you can enable globals: true in your vitest.config.ts. Use a setupFiles array to mock global browser APIs (like fetch or localStorage) before any tests run.

Architecture & Scaling

Worker Threads

Vitest runs tests in isolated worker threads. This prevents global state mutations in one test from leaking and corrupting another test. This parallel execution is why Vitest is so fast.

Error Recovery

If tests randomly timeout in CI but pass locally, it is likely because your CI pipeline has significantly fewer CPU cores than your M-series MacBook. Use poolOptions: { threads: { maxThreads: 2 } } in CI to prevent thrashing.

Security Notes

Tests often require API keys. Never commit real API keys to .env.test. Always use msw (Mock Service Worker) to intercept network requests at the network level and return stubbed JSON responses, guaranteeing your test suite never hits real infrastructure.

References

• Vitest Docs

Why use this skill

Use this when your agent works with vitest — structured patterns beat pasted docs and prevent common hallucinations.

AI pitfalls

• Referencing CLI flags or config keys that do not exist
• Using outdated major versions of tools
• Skipping lockfile or version pinning in examples

Production checklist

• Secrets in environment variables, not source code
• Error handling and logging in place
• Rate limits and timeouts configured

Related skills

• playwright — works well with
• react — works well with

Last Verified: 2026-07-02