vitest
Vitest fast unit testing framework powered by Vite with Jest-compatible API. Use when writing tests, mocking, configuring coverage, or working with test filtering and fixtures.
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About vitest
Vitest is a high-performance unit testing framework built on top of Vite, designed to provide developers with a fast and efficient way to write, run, and maintain tests for JavaScript and TypeScript projects. It addresses the common challenges of slow test execution and complex configuration by leveraging Vite's native build and transformation pipeline. Vitest offers a Jest-compatible API, making it a seamless drop-in replacement for projects already using Jest, while providing enhanced speed and modern features out of the box. The framework supports native ESM, TypeScript, and JSX, eliminating the need for additional setup and configuration for modern frontend projects.
Vitest comes packed with a wide range of features for comprehensive testing. It includes smart watch mode that reruns only affected tests, multi-threaded workers for parallel execution, and built-in code coverage tools using V8 or Istanbul. The framework supports snapshot testing, mocking, and spy utilities, as well as test filtering by name, file patterns, or tags. Its API encompasses core functionalities such as test, describe, and expect functions, along with hooks like beforeEach, afterEach, beforeAll, and afterAll. Advanced features include type-level testing, multi-project workspace support, and flexible test environments including Node, jsdom, and custom setups.
Vitest is ideal for frontend developers and teams working with modern JavaScript and TypeScript applications who need fast, reliable, and maintainable test suites. It is particularly suited for projects that already use Vite, allowing seamless integration without additional configuration overhead. Use cases include unit testing, mocking modules, snapshot testing, parallel test execution, and code coverage reporting. Its compatibility with Jest APIs makes it an attractive choice for migrating existing test suites while taking advantage of modern build tools and faster feedback loops during development.
FAQ
How do I integrate Vitest with an existing Vite project?
Vitest integrates directly with Vite projects by sharing the same configuration, transformers, resolvers, and plugins. You can use defineConfig in your Vitest configuration to align with your existing Vite setup.
Is Vitest compatible with Jest test suites?
Yes, Vitest provides a Jest-compatible API, allowing most Jest test suites to run with minimal changes. This includes functions like test, describe, and expect, as well as mocking and snapshot utilities.
Can Vitest run tests in parallel?
Yes, Vitest supports multi-threaded workers for parallel test execution, including concurrent tests, sharding, and smart watch mode to rerun only affected tests for improved efficiency.
Which test environments does Vitest support?
Vitest supports multiple environments such as Node, jsdom, happy-dom, and custom environments, allowing developers to test both frontend and backend scenarios with appropriate context.
Do I need additional configuration for TypeScript or JSX support?
No, Vitest supports TypeScript and JSX natively without additional configuration, enabling you to write and run tests in modern frontend codebases out of the box.
All Files
18 filesInstall vitest
Quick Setup:
- Copy the skill folder to
.claude/skills/ - Claude will automatically detect and use the skill
Repository
antfu/skills