Vitest

ELI5 — The Vibe Check

Vitest is a blazing-fast test runner built on Vite. If Jest is the reliable sedan, Vitest is the electric sports car — same driving experience, 10x faster. It's Jest-compatible (same API, same expect), so migrating is trivial. But because it uses Vite under the hood, it understands your project's config, supports TypeScript natively, and runs tests in parallel with near-instant startup.

Real Talk

Vitest is a Vite-native unit testing framework that provides a Jest-compatible API with significantly better performance through Vite's dev server and HMR capabilities. Features include native TypeScript/ESM support, in-source testing, browser mode, UI dashboard, code coverage (v8/istanbul), snapshot testing, and workspace support for monorepos. It shares Vite's config (aliases, plugins, transforms), eliminating the need for separate test configuration.

Show Me The Code

// math.test.ts
import { describe, it, expect } from 'vitest';
import { add, multiply } from './math';

describe('math', () => {
  it('adds two numbers', () => {
    expect(add(2, 3)).toBe(5);
  });

  it('multiplies two numbers', () => {
    expect(multiply(4, 5)).toBe(20);
  });
});

When You'll Hear This

"We switched from Jest to Vitest — tests run 5x faster with zero config." / "Vitest shares the Vite config, so aliases and transforms just work."