Features
- Zero-config testing for most JavaScript projects
- Built-in mocking, assertions, and code coverage
- Snapshot testing for UI components
- Parallel test execution across workers
Pros
- Largest ecosystem of matchers and plugins
- Battle-tested in production across thousands of projects
- Excellent documentation and community support
Cons
- Slower than Vitest, especially with TypeScript
- ESM support requires additional configuration
- Can be memory-heavy for large test suites
Overview
Jest is a JavaScript testing framework created by Meta (Facebook). It has been the dominant testing framework in the JavaScript ecosystem for years, used by React, numerous open-source projects, and countless production applications. Jest provides a complete testing solution with built-in assertions, mocking, code coverage, and snapshot testing.
Jest’s “zero-config” philosophy means it works out of the box for most projects. It automatically finds test files, provides a global API (describe, it, expect), and includes everything needed for comprehensive testing without additional packages.
While Vitest has gained momentum for Vite-based projects, Jest remains the most widely used and battle-tested JavaScript testing framework with the largest ecosystem of matchers, plugins, and community knowledge.
When to Use
Choose Jest for non-Vite projects, especially those using Webpack or Create React App. It is also the right choice when you need maximum ecosystem compatibility or are working with a team already familiar with Jest.
Getting Started
npm install --save-dev jest @types/jest ts-jest
npx jest --init
npx jest