Vitest

Use these conventions for testing JavaScript/TypeScript projects with vitest-dev/vitest.

Source Baseline

Prefer official docs at vitest.dev and the matching GitHub release over older Jest-era snippets.
Current stable baseline checked for this skill: Vitest 4.1.11 (August 2026). Vitest 5.0.0-rc.2 exists but is not the stable latest tag.
Vitest 4.1.11 supports Vite ^6.0.0 || ^7.0.0 || ^8.0.0 and Node.js ^20.0.0 || ^22.0.0 || >=24.0.0.
Treat main branch README/package metadata as prerelease when it disagrees with latest; use npm dist-tags.latest plus the versioned docs for stable support floors.
Vitest 4.1.11 tightens mocker redirect handling to the filesystem allowlist; do not rely on redirect-based mocks outside the configured allowlist.
Vitest is Vite-native: it reuses the project's Vite config, transforms, and resolvers — do not bolt Babel on top unless a transform is missing.
Vitest's vi API is Jest-compatible enough that most jest.* calls map 1:1 to vi.*, but the runtime, ESM handling, and mocking semantics differ — do not assume Jest behavior.

pnpm add -D vitest