Chai vs Vitest comparison of testing frameworks
What are the differences between Chai and Vitest?

Unit Testing

Unit testing, integration testing, and component testing

Chai is a BDD / TDD assertion library for Node.js and the browser that can be paired with any JavaScript testing framework.

Chai is an assertion library, similar to Node's built-in assert and makes testing easier by giving you many assertions you can run against your code. It also includes a robust Plugin architecture for extending Chai's assertions and interfaces.

Vitest is a fast, modern JavaScript test runner built on Vite

It supports unit, integration, and component testing with a Jest-compatible API, built-in mocking, and TypeScript support. Designed for speed and efficiency. It seamlessly integrates with Vite projects but can also be used independently.

N/A

No

Vitest does not natively follow the xUnit test structure, but it supports similar concepts. It uses a Jest-compatible API, meaning it provides test lifecycle hooks (beforeEach, afterEach, etc.) and assertions similar to xUnit-style frameworks. However, it does not strictly adhere to classical xUnit architecture, such as NUnit, JUnit, or MSTest.

Yes

Chai can be used in a browser environment to test front-end components and functionality

Yes

Vitest uses JSDOM to simulate a browser environment, making it easy to test DOM-related functionality. It has Browser Mode for running component tests in the browser. Vitest can run tests in real browsers via tools like Playwright or WebdriverIO.

Yes

Chai is used in a Node.JS environment to test server behaviour and functionality

Yes

Vitest supports server-side testing, allowing you to test Node.js and server-side logic such as APIs, databases, and backend functions. It provides native support for ESM, mocks, spies, and environment configurations.

N/A

Yes

Vitest's Test Context, inspired by Playwright Fixtures, allows defining utils, states, and fixtures for use in tests. It enables sharing context between tests using the test.context object and supports tuple syntax for fixtures, allowing customization of fixture options per test.

N/A

Yes

Vitest supports group fixtures by using describe blocks with beforeAll, beforeEach, afterEach, and afterAll hooks. These hooks allow setting up a shared state for a group of tests.

Yes

By using chai-spec-generator plugin which will generate chai test specs from a JavaScript object

No

MIT License

MIT License

Yes

By using by using a third party library like chai-jest-mocks which is a chai plugin that adds assertions for jest mock functions. You can also use sinon.js

Yes

Vitest has built-in support for mocks, allowing you to mock functions, modules, timers, and spies similar to Jest.

N/A

Yes

Vitest supports Grouping, allowing you to organize tests into groups using describe() blocks.

Vitest provides a watch mode for instant test re-runs, ESM-first architecture for modern development, parallel and concurrent test execution for speed, custom reporters for CI/CD integration, and fake timers for testing time-dependent code.