Getting Started

Overview

Vitest (pronounced as "veetest") is a next generation testing framework powered by Vite.

You can learn more about the rationale behind the project in the Why Vitest section.

Trying Vitest Online

You can try Vitest online on StackBlitz. It runs Vitest directly in the browser, and it is almost identical to the local setup but doesn't require installing anything on your machine.

Adding Vitest to Your Project

Learn how to install by Video

npm

npm install -D vitest

yarn

yarn add -D vitest

pnpm

pnpm add -D vitest

bun

bun add -D vitest

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Vitest requires Vite >=v5.0.0 and Node >=v18.0.0

It is recommended that you install a copy of vitest in your package.json, using one of the methods listed above. However, if you would prefer to run vitest directly, you can use npx vitest (the npx tool comes with npm and Node.js).

The npx tool will execute the specified command. By default, npx will first check if the command exists in the local project's binaries. If it is not found there, npx will look in the system's $PATH and execute it if found. If the command is not found in either location, npx will install it in a temporary location prior to execution.

Writing Tests

As an example, we will write a simple test that verifies the output of a function that adds two numbers.

// sum.js
export function sum(a, b) {
  return a + b
}

// sum.test.js
import { expect, test } from 'vitest'
import { sum } from './sum.js'

test('adds 1 + 2 to equal 3', () => {
  expect(sum(1, 2)).toBe(3)
})

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By default, tests must contain ".test." or ".spec." in their file name.

Next, in order to execute the test, add the following section to your package.json:

{
  "scripts": {
    "test": "vitest"
  }
}

Finally, run npm run test, yarn test or pnpm test, depending on your package manager, and Vitest will print this message:

✓ sum.test.js (1)
  ✓ adds 1 + 2 to equal 3

Test Files  1 passed (1)
     Tests  1 passed (1)
  Start at  02:15:44
  Duration  311ms

WARNING

If you are using Bun as your package manager, make sure to use bun run test command instead of bun test, otherwise Bun will run its own test runner.

Learn more about the usage of Vitest, see the API section.

Configuring Vitest

One of the main advantages of Vitest is its unified configuration with Vite. If present, vitest will read your root vite.config.ts to match with the plugins and setup as your Vite app. For example, your Vite resolve.alias and plugins configuration will work out-of-the-box. If you want a different configuration during testing, you can:

• Create vitest.config.ts, which will have the higher priority
• Pass --config option to CLI, e.g. vitest --config ./path/to/vitest.config.ts
• Use process.env.VITEST or mode property on defineConfig (will be set to test if not overridden) to conditionally apply different configuration in vite.config.ts

Vitest supports the same extensions for your configuration file as Vite does: .js, .mjs, .cjs, .ts, .cts, .mts. Vitest does not support .json extension.

If you are not using Vite as your build tool, you can configure Vitest using the test property in your config file:

import { defineConfig } from 'vitest/config'

export default defineConfig({
  test: {
    // ...
  },
})

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Even if you do not use Vite yourself, Vitest relies heavily on it for its transformation pipeline. For that reason, you can also configure any property described in Vite documentation.

If you are already using Vite, add test property in your Vite config. You'll also need to add a reference to Vitest types using a triple slash directive at the top of your config file.

/// <reference types="vitest" />
import { defineConfig } from 'vite'

export default defineConfig({
  test: {
    // ...
  },
})

The <reference types="vitest" /> will stop working in Vitest 3, but you can start migrating to vitest/config in Vitest 2.1:

/// <reference types="vitest/config" />
import { defineConfig } from 'vite'

export default defineConfig({
  test: {
    // ... Specify options here.
  },
})

See the list of config options in the Config Reference

WARNING

If you decide to have two separate config files for Vite and Vitest, make sure to define the same Vite options in your Vitest config file since it will override your Vite file, not extend it. You can also use mergeConfig method from vite or vitest/config entries to merge Vite config with Vitest config:

vitest.config.mjs

import { defineConfig, mergeConfig } from 'vitest/config'
import viteConfig from './vite.config.mjs'

export default mergeConfig(viteConfig, defineConfig({
  test: {
    // ...
  },
}))

vite.config.mjs

import { defineConfig } from 'vite'
import Vue from '@vitejs/plugin-vue'

export default defineConfig({
  plugins: [Vue()],
})

However, we recommend using the same file for both Vite and Vitest, instead of creating two separate files.

Workspaces Support

Run different project configurations inside the same project with Vitest Workspaces. You can define a list of files and folders that define your workspace in vitest.workspace file. The file supports js/ts/json extensions. This feature works great with monorepo setups.

import { defineWorkspace } from 'vitest/config'

export default defineWorkspace([
  // you can use a list of glob patterns to define your workspaces
  // Vitest expects a list of config files
  // or directories where there is a config file
  'packages/*',
  'tests/*/vitest.config.{e2e,unit}.ts',
  // you can even run the same tests,
  // but with different configs in the same "vitest" process
  {
    test: {
      name: 'happy-dom',
      root: './shared_tests',
      environment: 'happy-dom',
      setupFiles: ['./setup.happy-dom.ts'],
    },
  },
  {
    test: {
      name: 'node',
      root: './shared_tests',
      environment: 'node',
      setupFiles: ['./setup.node.ts'],
    },
  },
])

Command Line Interface

In a project where Vitest is installed, you can use the vitest binary in your npm scripts, or run it directly with npx vitest. Here are the default npm scripts in a scaffolded Vitest project:

{
  "scripts": {
    "test": "vitest",
    "coverage": "vitest run --coverage"
  }
}

To run tests once without watching for file changes, use vitest run. You can specify additional CLI options like --port or --https. For a full list of CLI options, run npx vitest --help in your project.

Learn more about the Command Line Interface

Automatic Dependency Installation

Vitest will prompt you to install certain dependencies if they are not already installed. You can disable this behavior by setting the VITEST_SKIP_INSTALL_CHECKS=1 environment variable.

IDE Integrations

We also provided a official extension for Visual Studio Code to enhance your testing experience with Vitest.

Install from VS Code Marketplace

Learn more about IDE Integrations

Examples

Example	Source	Playground
basic	GitHub	Play Online
fastify	GitHub	Play Online
in-source-test	GitHub	Play Online
lit	GitHub	Play Online
vue	GitHub	Play Online
marko	GitHub	Play Online
preact	GitHub	Play Online
react	GitHub	Play Online
solid	GitHub	Play Online
svelte	GitHub	Play Online
sveltekit	GitHub	Play Online
profiling	GitHub	Not Available
typecheck	GitHub	Play Online
workspace	GitHub	Play Online

Projects using Vitest

• unocss
• unplugin-auto-import
• unplugin-vue-components
• vue
• vite
• vitesse
• vitesse-lite
• fluent-vue
• vueuse
• milkdown
• gridjs-svelte
• spring-easing
• bytemd
• faker
• million
• Vitamin
• neodrag
• svelte-multiselect
• iconify
• tdesign-vue-next
• cz-git

Using Unreleased Commits

Each commit on main branch and a PR with a cr-tracked label are published to pkg.pr.new. You can install it by npm i https://pkg.pr.new/vitest@{commit}.

If you want to test your own modification locally, you can build and link it yourself (pnpm is required):

git clone https://github.com/vitest-dev/vitest.git
cd vitest
pnpm install
cd packages/vitest
pnpm run build
pnpm link --global # you can use your preferred package manager for this step

Then go to the project where you are using Vitest and run pnpm link --global vitest (or the package manager that you used to link vitest globally).

Community

If you have questions or need help, reach out to the community at Discord and GitHub Discussions.