vitest
Installation
Summary
Vite-powered unit testing framework with Jest-compatible API and native ESM support.
- Shares Vite's config, transformers, and plugins; supports TypeScript, JSX, and ESM without extra setup
- Smart watch mode reruns only affected tests based on module graph; multi-threaded workers enable parallel execution
- Comprehensive testing utilities: test/describe/expect API, mocking (functions, modules, timers), snapshots, and fixtures
- Built-in code coverage via V8 or Istanbul; test filtering by name, file patterns, and tags
- Advanced features include type-level testing, custom environments (node, jsdom, happy-dom), and multi-project workspaces
SKILL.md
Vitest is a next-generation testing framework powered by Vite. It provides a Jest-compatible API with native ESM, TypeScript, and JSX support out of the box. Vitest shares the same config, transformers, resolvers, and plugins with your Vite app.
Key Features:
- Vite-native: Uses Vite's transformation pipeline for fast HMR-like test updates
- Jest-compatible: Drop-in replacement for most Jest test suites
- Smart watch mode: Only reruns affected tests based on module graph
- Native ESM, TypeScript, JSX support without configuration
- Multi-threaded workers for parallel test execution
- Built-in coverage via V8 or Istanbul
- Snapshot testing, mocking, and spy utilities
The skill is based on Vitest 3.x, generated at 2026-01-28.