Mocha vs Web Test Runner

Mocha is a free, open-source JavaScript test framework that runs in Node.js and browsers. Tests run serially by default, and uncaught exceptions are associated with their test cases. Asynchronous tests can use callbacks or returned promises, while parallel execution is available in Node.js but not in browsers. The command-line interface defaults to the BDD interface and spec reporter; browser runs default to the HTML reporter, and reporters can be configured. Installation as a development dependency is documented for npm, pnpm, and yarn. Mocha 12 requires Node.js ^20.19.0 or >=22.12.0, and browser builds document support for evergreen Chrome, Edge, Firefox, and Safari. It supports JavaScript and TypeScript, parameterized cases, and lists editor-related packages for TextMate, JetBrains IDEs, Wallaby.js, Emacs, and VS Code. Built-in mocks are not included. The project points users to Discord and documentation explainers for more information.

Web Test Runner is a test runner for web applications, installable as an npm development dependency. It runs tests in parallel and isolation, giving each test file its own browser environment. Headless testing is supported through launchers including Puppeteer, Playwright, Selenium, BrowserStack, and WebdriverIO. Playwright can use Chromium, Firefox, and WebKit; BrowserStack runs tests remotely, including against older browser versions. Debug mode opens a browser window with developer tools, and the runner reports browser logs, 404 responses, and errors. Its command line offers interactive watch mode that reruns tests when files change, plus code coverage with configurable thresholds and reports. Default coverage instrumentation uses Chromium. Other features include ES module mocking through import maps and Mocha integration, with guidance for a custom test framework. The project is MIT-licensed, powered by esbuild and Rollup plugins, and directs users to GitHub and Discord for help and discussion. It is free and open source.