Vitest Cheatsheet

Setup

Use this Vitest reference while you build software engineering projects, review code for technical interview prep, or polish examples for a software engineer resume.

Vitest Cheatsheet Overview

Use this Vitest cheatsheet as a fast developer reference for JavaScript and React unit tests: install the runner, choose Node or jsdom, wire scripts, and keep common CLI flags close while coding. If you are building a broader programming cheatsheet stack, pair it with the React cheatsheet, Python cheatsheet, SQL cheatsheet, and Git cheatsheet for framework, language, database, and workflow syntax.

Installation

# npm
npm install -D vitest

# yarn
yarn add -D vitest

# pnpm
pnpm add -D vitest

For browser-mode or jsdom environments, add the appropriate environment package:

npm install -D @vitest/ui @vitest/coverage-v8 jsdom happy-dom

package.json Scripts

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

Minimal Config (vite.config.ts)

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

export default defineConfig({
  test: {
    globals: true,
    environment: 'node', // 'jsdom' | 'happy-dom' | 'edge-runtime'
  },
})

Dedicated vitest.config.ts

import { defineConfig } from 'vitest/config'

export default defineConfig({
  test: {
    globals: true,
    environment: 'jsdom',
    setupFiles: ['./src/test/setup.ts'],
    include: ['src/**/*.{test,spec}.{ts,tsx}'],
    exclude: ['node_modules', 'dist', 'e2e/**'],
  },
})

Use vitest/config (not vite) when you don't need a Vite build config — it avoids pulling in unnecessary plugins.

TypeScript: Global Types Without Importing

Add globals: true in config, then reference the types:

// tsconfig.json
{
  "compilerOptions": {
    "types": ["vitest/globals"]
  }
}

Or add a triple-slash reference in a vitest.d.ts:

/// <reference types="vitest/globals" />

Projects (Monorepo)

Define projects in the root vitest.config.ts under test.projects — glob strings and/or inline configs:

// vitest.config.ts
import { defineConfig } from 'vitest/config'

export default defineConfig({
  test: {
    projects: [
      'packages/*/vitest.config.ts',
      {
        test: {
          name: 'browser',
          environment: 'happy-dom',
          include: ['src/**/*.browser.test.ts'],
        },
      },
    ],
  },
})

Run a specific project:

vitest --project browser

Legacy: vitest.workspace.ts / defineWorkspace were deprecated in Vitest 3.2 and removed in Vitest 4 — move the array into test.projects.

Environment Selection Per File

// @vitest-environment jsdom

import { describe, it, expect } from 'vitest'

describe('DOM test', () => {
  it('has a document', () => {
    expect(document).toBeDefined()
  })
})

Supported docblock values: node, jsdom, happy-dom, edge-runtime.

CLI Flags Reference

Flag	Description
`--watch`	Re-run on file change (default in dev)
`--run`	Single run, no watch (default in CI)
`--ui`	Launch the Vitest UI
`--coverage`	Collect coverage
`--reporter=verbose`	Verbose output
`--reporter=dot`	Dot output
`--reporter=json`	JSON output to stdout
`--outputFile=out.json`	Write reporter output to file
`--testNamePattern=<regex>`	Filter tests by name
`--project <name>`	Run a specific project
`--shard=1/4`	Run shard 1 of 4 (CI parallelism)
`--pool=forks`	Use child processes instead of threads
`--no-file-parallelism`	Run test files sequentially
`--bail=1`	Stop after N failures
`--changed`	Only run tests for changed files
`--passWithNoTests`	Exit 0 when no tests found