This directory contains tests for HTML.
Sub-directory names should be based on the URL of the corresponding part of the multipage-version specification. For example, the URL of "8.3 Base64 utility methods" is https://html.spec.whatwg.org/multipage/webappapis.html#atob. So the directory in WPT is webappapis/atob/.
For historical reasons, parts of HTML have their own directories: