A framework for React
Facebook develops Jest internally to test its own JavaScript codebases — React included. Before Jest, Node testing is fragmented: Mocha + Chai + Sinon, Jasmine, AVA, Tape each with different syntax and assembly. Configuring and running takes a lot of setup.
The release
Jest is open-sourced by Facebook in 2014; versions 14.0 (May 2016) and 16.0 (September 2016) mark the transformation into a mass framework with adoption by Create React App. Main author: Christoph Nakazawa. MIT licence. Since 2022 maintained by Meta but donated to OpenJS Foundation.
test('sum adds numbers', () => {
expect(sum(1, 2)).toBe(3);
});
test('user snapshot', () => {
expect(renderUser()).toMatchSnapshot();
});Features
- Zero config — works out-of-box with ES modules, JSX, TypeScript (via babel-jest)
- Integrated assertion library —
expect()with.toBe(),.toEqual(),.toMatch(),.toThrow()matchers - Built-in mocking —
jest.fn(),jest.mock()for modules - Snapshot testing — serialises output and compares on subsequent runs
- Parallel execution — worker pool for parallel tests
- Code coverage — integrated Istanbul with
--coverage - Watch mode — interactive, re-runs only affected tests
- jsdom environment integrated for DOM tests
React Testing Library
In 2018 Kent C. Dodds releases @testing-library/react, which replaces the lower-level Enzyme (Airbnb). The combination Jest + React Testing Library has been the de facto standard for React testing since 2019.
Competitors
- Mocha + Chai — historical, more configurable and less opinionated
- AVA — concurrent, minimal
- Jasmine — older
- Vitest (2021, born with Vite) — Jest-compatible API, very fast, ESM-first; replacing Jest in many new projects
- Node Test Runner (Node 20+) — built-in, minimal
- Bun test — ultra-fast
In the Italian context
Jest has been the de facto standard of Italian React teams since 2018. Used in:
- Italian headless e-commerce (Magento, Shopify storefront)
- Fintech — crypto web apps, neobanks
- Digital PA — PagoPA, App IO, Design System Italia projects
- B2B SaaS
From 2023 there is a progressive transition to Vitest in new Vite-based projects.
References: Jest (Facebook, open source 2014). Christoph Nakazawa lead. MIT licence. Donated to OpenJS Foundation (2022). React Testing Library (Kent C. Dodds, 2018) React testing standard. Vitest (2021) Jest-compatible replacement.