Karma vs Rstest

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.

Rstest is a free, open-source testing framework for JavaScript and TypeScript, built on Rsbuild and Rspack. It bundles tests through Rspack’s dependency-graph build process and applies SWC transforms. Projects can reuse configuration from Rsbuild, Rslib, or Rspack, including aliases, transforms, and plugins. Tests run in Node.js, simulated DOM environments with jsdom or happy-dom, and real browsers. Browser Mode uses Playwright to run tests in Chromium, Firefox, and WebKit; an integration supports end-to-end tests against local, preview, or deployed URLs. Rstest can also load Module Federation remotes in Node, JSDOM, and Browser Mode. Its built-in tools include Jest-compatible assertions, snapshots, mocks, spies, lifecycle hooks, file-level isolation, reporters, filtering, and coverage reporting. For CI, it supports multi-project testing, sharding, blob report merging, and coverage thresholds. The Rstack VS Code extension lets users browse, run, and debug tests. The quick start requires Node.js 20.19.0 or newer, and recommends the Node.js LTS version. Rstest is released under the MIT license.