vitest

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

INSTALLATION
npx skills add https://github.com/antfu/skills --skill vitest
Run in your project or agent environment. Adjust flags if your CLI version differs.

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.

Core

Topic

Description

Reference

Configuration

Vitest and Vite config integration, defineConfig usage

core-config

CLI

Command line interface, commands and options

core-cli

Test API

test/it function, modifiers like skip, only, concurrent

core-test-api

Describe API

describe/suite for grouping tests and nested suites

core-describe

Expect API

Assertions with toBe, toEqual, matchers and asymmetric matchers

core-expect

Hooks

beforeEach, afterEach, beforeAll, afterAll, aroundEach

core-hooks

Features

Topic

Description

Reference

Mocking

Mock functions, modules, timers, dates with vi utilities

features-mocking

Snapshots

Snapshot testing with toMatchSnapshot and inline snapshots

features-snapshots

Coverage

Code coverage with V8 or Istanbul providers

features-coverage

Test Context

Test fixtures, context.expect, test.extend for custom fixtures

features-context

Concurrency

Concurrent tests, parallel execution, sharding

features-concurrency

Filtering

Filter tests by name, file patterns, tags

features-filtering

Advanced

Topic

Description

Reference

Vi Utilities

vi helper: mock, spyOn, fake timers, hoisted, waitFor

advanced-vi

Environments

Test environments: node, jsdom, happy-dom, custom

advanced-environments

Type Testing

Type-level testing with expectTypeOf and assertType

advanced-type-testing

Projects

Multi-project workspaces, different configs per project

advanced-projects

BrowserAct

Let your agent run on any real-world website

Bypass CAPTCHA & anti-bot for free. Start local, scale to cloud.

Explore BrowserAct Skills →

Stop writing automation&scrapers

Install the CLI. Run your first Skill in 30 seconds. Scale when you're ready.

Start free
free · no credit card