The jsdom project uses two different test frameworks:

• web-platform-tests. They come in the form of .html files which are run inside the jsdom. This is part of a large cross-browser testing effort that jsdom is participating in.
• Mocha tests

For working on new tests:

• Tests for web platform features go in the web-platform-tests/to-upstream subdirectory. This should be the majority of new work.
• Tests for the jsdom API itself go in the api subdirectory. If you add a new test file, edit index.js to include it.

Ignore all the rest.

All Mocha tests are run via the file index.js. This includes running web-platform-tests, which are wrapped as Mocha tests.

All files related to running web-platform-tests are inside the web-platform-tests subdirectory.

Ideally we would only use Mocha for testing the JSDOM API itself, from the outside. Unfortunately, a lot of web platform features are still tested using Mocha, instead of web-platform-tests. These are located in the to-port-to-wpts subdirectory.