Vitest
Anthony FuCommunityCreated by Anthony Fu
- Skill
- Tool integration
- Software development
- MIT
- No issues found
AutoGineer summary
Written by AutoGineer from the skill’s own files, not by the author
Vitest is a testing framework built for the Vite ecosystem. It provides a Jest-compatible API and supports ESM, TypeScript, and JSX by default. It shares configuration, transformers, and plugins with Vite applications, allowing for integrated testing workflows. The framework includes features for mocking, snapshot testing, code coverage, and multi-threaded test execution.
What it does
- Provides a Jest-compatible API for writing and running unit tests
- Supports native ESM, TypeScript, and JSX without additional configuration
- Enables mocking of functions, modules, timers, and dates
- Offers built-in code coverage reporting using V8 or Istanbul
- Supports multi-project workspaces and varied test environments like Node, jsdom, and happy-dom
- Includes utilities for snapshot testing, test filtering, and benchmarking
When to use it
- When you need a testing framework that integrates directly with your Vite configuration
- When migrating existing test suites that rely on Jest-compatible APIs
- When you require specific test environments like jsdom or happy-dom for DOM-related testing
- When managing complex test setups across monorepos or multiple projects
Advantages
- Shares configuration and plugins with Vite projects
- Supports parallel test execution via multi-threaded workers
- Provides flexible test environment configuration per file or project
- Includes built-in support for snapshot testing and mocking utilities
Usage examples
- “How do I configure Vitest to use the jsdom environment for my tests?”
- The agent provides the vitest.config.ts configuration snippet using the environment: 'jsdom' property and explains how to install the necessary jsdom package.
- “Can I run different test configurations in the same Vitest process?”
- The agent explains how to use the projects field in the vitest.config.ts file to define multiple test suites with different environments or include patterns.
Install
Download the skill as a ZIP:
https://mp-staging.autogineer.com/agent-skills/antfu/vitest/downloadUnzip it into the cross-client skills folder of your project:
mkdir -p .agents/skills && unzip vitest.zip -d .agents/skills
Documentation by Anthony Fu
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 |
| 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 |
| Test Tags | Label tests with tags to filter runs and apply shared options | features-test-tags |
| Reporters | Built-in reporters, default selection, CI/output config | features-reporters |
| Benchmarking | Write benchmarks with the bench fixture (Tinybench) | features-benchmarking |
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 |
Files
- ATTRIBUTION.mdAdded by AutoGineer895 B
- GENERATION.md136 B
- LICENSELicence file added by AutoGineer1.1 KiB
- SKILL.md3.6 KiB
- references/advanced-environments.md4.9 KiB
- references/advanced-projects.md7.4 KiB
- references/advanced-type-testing.md4.6 KiB
- references/advanced-vi.md5.8 KiB
- references/core-cli.md4.9 KiB
- references/core-config.md7.7 KiB
- references/core-describe.md3.5 KiB
- references/core-expect.md8.8 KiB
- references/core-hooks.md4.8 KiB
- references/core-test-api.md5.5 KiB
- references/features-benchmarking.md3.9 KiB
- references/features-concurrency.md4.7 KiB
- references/features-context.md5.3 KiB
- references/features-coverage.md5.0 KiB
- references/features-filtering.md4.8 KiB
- references/features-mocking.md9.8 KiB
- references/features-reporters.md4.0 KiB
- references/features-snapshots.md5.2 KiB
- references/features-test-tags.md3.6 KiB
references/core-hooks.md
name: lifecycle-hooks description: beforeEach, afterEach, beforeAll, afterAll, and around hooks
Lifecycle Hooks
Basic Hooks
import { afterAll, afterEach, beforeAll, beforeEach, test } from 'vitest'
beforeAll(async () => {
// Runs once before all tests in file/suite
await setupDatabase()
})
afterAll(async () => {
// Runs once after all tests in file/suite
await teardownDatabase()
})
beforeEach(async () => {
// Runs before each test
await clearTestData()
})
afterEach(async () => {
// Runs after each test
await cleanupMocks()
})Cleanup Return Pattern
Return cleanup function from before* hooks:
beforeAll(async () => {
const server = await startServer()
// Returned function runs as afterAll
return async () => {
await server.close()
}
})
beforeEach(async () => {
const connection = await connect()
// Runs as afterEach
return () => connection.close()
})Scoped Hooks
Hooks apply to current suite and nested suites:
describe('outer', () => {
beforeEach(() => console.log('outer before'))
test('test 1', () => {}) // outer before → test
describe('inner', () => {
beforeEach(() => console.log('inner before'))
test('test 2', () => {}) // outer before → inner before → test
})
})Hook Timeout
beforeAll(async () => {
await slowSetup()
}, 30_000) // 30 second timeoutAround Hooks
Wrap tests with setup/teardown context:
import { aroundEach, test } from 'vitest'
// Wrap each test in database transaction
aroundEach(async (runTest) => {
await db.beginTransaction()
await runTest() // Must be called!
await db.rollback()
})
test('insert user', async () => {
await db.insert({ name: 'Alice' })
// Automatically rolled back after test
})aroundAll
Wrap entire suite:
import { aroundAll, test } from 'vitest'
aroundAll(async (runSuite) => {
console.log('before all tests')
await runSuite() // Must be called!
console.log('after all tests')
})Multiple Around Hooks
Nested like onion layers:
aroundEach(async (runTest) => {
console.log('outer before')
await runTest()
console.log('outer after')
})
aroundEach(async (runTest) => {
console.log('inner before')
await runTest()
console.log('inner after')
})
// Order: outer before → inner before → test → inner after → outer afterTest Hooks
Inside test body:
import { onTestFailed, onTestFinished, test } from 'vitest'
test('with cleanup', () => {
const db = connect()
// Runs after test finishes (pass or fail)
onTestFinished(() => db.close())
// Only runs if test fails
onTestFailed(({ task }) => {
console.log('Failed:', task.result?.errors)
})
db.query('SELECT * FROM users')
})Reusable Cleanup Pattern
function useTestDb() {
const db = connect()
onTestFinished(() => db.close())
return db
}
test('query users', () => {
const db = useTestDb()
expect(db.query('SELECT * FROM users')).toBeDefined()
})
test('query orders', () => {
const db = useTestDb() // Fresh connection, auto-closed
expect(db.query('SELECT * FROM orders')).toBeDefined()
})Concurrent Test Hooks
For concurrent tests, use context's hooks:
test.concurrent('concurrent', ({ onTestFinished }) => {
const resource = allocate()
onTestFinished(() => resource.release())
})Extended Test Hooks
With test.extend, hooks are type-aware and must be called on the extended test:
const test = base
.extend('db', { scope: 'file' }, async ({}, { onCleanup }) => {
const db = await createDb()
onCleanup(() => db.close())
return db
})
// Test-level hooks see fixtures
test.beforeEach(({ db }) => db.seed())
test.afterEach(({ db }) => db.clear())
// Suite-level hooks (4.1+) can access file/worker-scoped fixtures
test.beforeAll(({ db }) => db.createUsers())
test.aroundAll(async (runSuite, { db }) => db.transaction(runSuite))Suite-level hooks (beforeAll/afterAll/aroundAll) only see file/worker-scoped fixtures, and the global beforeAll/afterAll cannot access custom fixtures — use test.beforeAll etc.
Hook Execution Order
Default order (stack):
beforeAll(in order)beforeEach(in order)Test
afterEach(reverse order)afterAll(reverse order)
Configure with sequence.hooks:
defineConfig({
test: {
sequence: {
hooks: 'list', // 'stack' (default), 'list', 'parallel'
},
},
})Key Points
Hooks are not called during type checking
Return cleanup function from
before*to avoidafter*duplicationaroundEach/aroundAllmust callrunTest()/runSuite()onTestFinishedalways runs, even if test failsUse context hooks for concurrent tests
<!-- Source references: - https://vitest.dev/api/hooks.html -->
Requirements and compatibility
Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta
“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.
Needs: Needs Node.js
Security
No issues found by our static scan· No issues found
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Attribution and licence
- Created by
- Anthony Fu
- Publisher
- Anthony Fu (Community)
- Source
- antfu/skills · skills/vitest · commit f63e9ec
- Licence
- MIT License (redistribution allowed)
- LICENSE (added by AutoGineer from LICENSE.md)
- ATTRIBUTION.md (written by AutoGineer)
- Synced
AutoGineer is not affiliated with or endorsed by Anthony Fu.
Download ZIP
The ZIP holds the skill’s files, its licence files and an ATTRIBUTION.md. Download vitest.zip