# Vitest

Vitest fast unit testing framework powered by Vite with Jest-compatible API.

- Repository: https://github.com/antfu/skills (6032 stars)
- Category: Testing
- License: MIT
- Last updated: 2026-10-30
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add antfu/skills --skill vitest -g -a claude-code -y`
Codex: `npx skills add antfu/skills --skill vitest -g -a codex -y`
Cursor: `npx skills add antfu/skills --skill vitest -g -a cursor -y`
Gemini CLI: `npx skills add antfu/skills --skill vitest -g -a gemini-cli -y`

## Description

Vitest fast unit testing framework powered by Vite with Jest-compatible API. Use when writing tests, mocking, configuring coverage, or working with test filtering and fixtures.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

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 5.1.0-beta.1, generated at 2026-10-23.

## Core

| Topic | Description | Reference |
|-------|-------------|-----------|
| Configuration | Vitest and Vite config integration, defineConfig usage | [core-config](references/core-config.md) |
| CLI | Command line interface, commands and options | [core-cli](references/core-cli.md) |
| Test API | test/it function, modifiers like skip, only, concurrent | [core-test-api](references/core-test-api.md) |
| Describe API | describe/suite for grouping tests and nested suites | [core-describe](references/core-describe.md) |
| Expect API | Assertions with toBe, toEqual, matchers and asymmetric matchers | [core-expect](references/core-expect.md) |
| Hooks | beforeEach, afterEach, beforeAll, afterAll, aroundEach | [core-hooks](references/core-hooks.md) |

## Features

The rest: https://github.com/antfu/skills/blob/HEAD/skills/vitest/SKILL.md