vitest
Vite-powered unit testing framework with Jest-compatible API and native ESM support.
- Jest-compatible test syntax (test/describe/expect) with drop-in replacement capability for most Jest suites
- Native support for ESM, TypeScript, and JSX without additional configuration; shares Vite's transformation pipeline
- Smart watch mode reruns only affected tests based on module graph; multi-threaded workers enable parallel execution
- Built-in mocking (functions, modules, timers), snapshot testing, code coverage via V8 or Istanbul, and test filtering by name or tags
- Advanced features include test fixtures, concurrent test execution, type-level testing, and multi-project workspace support
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.
Core
| Topic | Description | Reference |
|---|---|---|
| Configuration | Vitest and Vite config integration, defineConfig usage | core-config |
| CLI | Command line interface, commands and options | core-cli |
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