Japa vs Karma

Japa is a free testing framework for Node.js backend applications and libraries, including JSON API and browser testing. Tests can be arranged into suites and groups with lifecycle hooks, filtering, asynchronous execution, datasets, snapshots, pinned tests, and bail mode. Assertion choices include Chai-based assert, Jest-style expect, and TypeScript type assertions. Its API client tests endpoints returning JSON, XML, HTML, or plain text, while an OpenAPI plugin checks responses against a schema. Browser testing uses a Playwright-based client with browser and context management, built-in assertions, and tracing options. Coverage reporting is documented with c8 or nyc. Japa has an official VS Code extension and an AdonisJS preset. It has no separate CLI; tests run from a configured entry point with Node.js or Bun. Setup occurs inside an existing Node.js project, where users select assertion libraries and optional plugins. Japa requires Node.js 18 or later, runs without transpilers, and works only with the ES module system.

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.