Vitest Has a Free Test Runner — Jest but 10x Faster With Native ESM

Jest Is Showing Its Age Jest was the gold standard for JavaScript testing. But in 2026, it struggles with ESM imports, needs Babel transforms, and runs slowly on large projects. Vitest: Vite-Powered Testing Vitest is a test runner powered by Vite. It reuses your Vite config, understands ESM natively, and runs tests blazingly fast. Speed Comparison Jest (500 tests): 12 seconds Vitest (500 tests): 1.5 seconds 8x faster. On watch mode, tests re-run in milliseconds because Vitest only transforms changed files. Jest-Compatible API import { describe , it , expect , vi } from ' vitest ' describe ( ' Calculator ' , () => { it ( ' adds numbers ' , () => { expect ( add ( 2 , 3 )). toBe ( 5 ) }) it ( ' mocks functions ' , () => { const fn = vi . fn (). mockReturnValue ( 42 ) expect ( fn ()). toBe ( 42 ) expect ( fn ). toHaveBeenCalledOnce () }) }) Same API as Jest. vi.fn() instead of jest.fn() . That is the only change for most tests. Why Developers Switch 1. Native ESM Support // This just works