Features
- Vite-native test runner with instant transforms
- Jest-compatible API for easy migration
- Built-in code coverage, mocking, and snapshots
- Watch mode with smart file detection
Pros
- Shares Vite config, no duplicate setup needed
- Significantly faster than Jest for Vite projects
- First-class TypeScript and ESM support
Cons
- Tied to Vite ecosystem for optimal performance
- Younger than Jest with smaller plugin ecosystem
- Browser mode is still evolving
Overview
Vitest is a unit testing framework built on top of Vite. It reuses Vite’s transform pipeline and dev server infrastructure to provide extremely fast test execution with native TypeScript and ESM support. If your project uses Vite, Vitest is the natural testing choice because it shares the same configuration.
Vitest provides a Jest-compatible API, making migration from Jest straightforward in most cases. It includes built-in support for mocking, code coverage (via v8 or Istanbul), snapshot testing, and concurrent test execution.
The watch mode is particularly impressive: it uses Vite’s module graph to determine which tests are affected by a file change and re-runs only those tests, providing near-instant feedback during development.
When to Use
Choose Vitest for any Vite-based project. It is also an excellent choice for non-Vite projects when you want fast test execution with native TypeScript and ESM support.
Getting Started
npm install --save-dev vitest
npx vitest