Karma vs Testem

Karma is a JavaScript test runner that starts a web server, connects browsers, runs tests, and reports results to developers. It can watch configured files and rerun tests when they change. Plugins connect frameworks such as Jasmine, Mocha, and QUnit, alongside preprocessors, reporters, and browser launchers. Documented launchers include Chrome, Firefox, Safari, PhantomJS, JSDOM, Opera, Internet Explorer, SauceLabs, and BrowserStack. A browser on another device on the same network, including a phone or tablet, can be captured by visiting the Karma server URL. Karma runs on Node.js and is distributed as an npm package; its installation guide recommends installing it locally in a project. Documentation includes integration guides for Travis CI, Jenkins, and Semaphore CI. The project describes Karma as primarily designed for low-level unit testing and points to Protractor for high-level testing. Karma is free and MIT-licensed, but deprecated: it accepts no new features or general bug fixes. Critical security fixes continue until 12 months after Angular CLI’s Web Test Runner support is marked stable.

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.