Vitest vs Jest for Next.js in 2026: Setup, Speed, and When to Switch

Jest has been the standard for years. Vitest is the new challenger. For Next.js projects in 2026, the answer is almost always Vitest -- here's why and how to set it up. Why Vitest Wins for Modern Next.js Speed: Vitest uses Vite's transform pipeline. Tests start 10-20x faster than Jest. No more waiting 8 seconds for the test runner to boot. Native ESM: Next.js 14 uses ES modules. Jest requires complex config to handle them. Vitest handles ESM natively. TypeScript out of the box: No ts-jest or babel-jest config needed. Jest compatibility: Vitest's API is Jest-compatible. describe, it, expect, beforeEach -- all the same. Most Jest tests run unmodified. Watch mode: Vitest's watch mode re-runs only changed tests using Vite's module graph. Instant feedback. Setup for Next.js npm install -D vitest @vitejs/plugin-react jsdom @testing-library/react @testing-library/jest-dom @testing-library/user-event // vitest.config.ts import { defineConfig } from 'vitest/config' import react from '@vitejs/pl