Jest vs Testem

Jest is a free, self-hosted JavaScript testing framework focused on checking correctness. It supports projects using Babel, TypeScript, Node, React, Angular, Vue and other technologies, and aims to run without configuration on most JavaScript projects. Snapshot tests compare rendered output with a saved reference. Tests run in separate processes for parallel execution, while the --coverage flag can collect coverage, including from files without tests. Mock functions and a custom import resolver support replacing objects and observing calls. Interactive watch mode reruns tests related to changed files. Installation guidance covers npm, Yarn, pnpm and Bun. Documentation describes webpack and Parcel use, but states that Vite is unsupported because of plugin-system incompatibilities. With Babel handling TypeScript, Jest transpiles tests without type-checking them during execution. A free plan is listed at free, with no paid plans or usage limits stated.

Testem is a JavaScript test runner for running tests in Node.js, real desktop browsers, or a launcher you configure. It supports Jasmine, QUnit, Mocha, and custom framework adapters, and can be used for unit, integration, end-to-end-style, or custom test setups. Browser runs can use Chrome, Firefox, Safari, or Edge, including a Headless Chrome launcher. In development mode, a terminal interface watches project files and reruns tests after relevant changes; CI mode can run tests in available browsers in parallel. Testem includes CI reporters for TAP, dot, xunit, and TeamCity, with custom reporters available. Listed preprocessing support includes Babel, TypeScript, Browserify, ESLint, JSHint, JSLint, and CoffeeScript. Its API provides startDev, startCI, and startServer modes, and coverage reporting is supported. It works with GitHub Actions, Jenkins, and TeamCity. Testem is free and open source under the MIT license, and runs on Linux, macOS, and Windows. It requires a supported Node.js runtime: ^22.17.0, ^24.0.0, or >=26.0.0.