vitest

Vitest

Next generation testing framework powered by Vite.

Quick Navigation

• Test API - test, describe, hooks
• Expect API - matchers and assertions
• Mocking - vi.fn, vi.mock, fake timers
• Configuration - vitest.config.ts options
• CLI - command line reference
• Browser Mode - real browser testing

When to Use

• Testing Vite-based applications (shared config)
• Need Jest-compatible API with native ESM support
• Component testing in real browser
• Fast watch mode with HMR
• TypeScript testing without extra config
• Parallel test execution

Installation

Install: npm install -D vitest. Requires Vite >=v6.0.0, Node >=v20.0.0.

Release Highlights (4.1.0 -> 4.1.6)

• New control-flow hooks: aroundEach and aroundAll.
• Test metadata expands with tags, meta, and improved test.extend type inference.
• CLI adds --detect-async-leaks, richer --update modes, and static collection for vitest list.
• Browser mode grows Playwright persistent contexts, userEvent.wheel, and stronger trace/artifact handling.
• Mocking/timers add disposable doMock(), mockThrow / mockThrowOnce, and setTickMode.
• 4.1.4 adds experimental ARIA snapshots, filterMeta for the JSON reporter, and exposes assertion as a public experimental field.
• 4.1.5 adds coverage instrumenter support and improves reporter/UI behavior around large snapshots and HTML output.
• 4.1.6 tightens browser screenshot path resolution and fixes sequence.concurrent handling for concurrent test scheduling.

Quick Start

// 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);
});

// package.json
{
  "scripts": {
    "test": "vitest",
    "test:run": "vitest run",
    "coverage": "vitest run --coverage"
  }
}