The Media Capabilities specification is available here: https://wicg.github.io/media-capabilities
GitHub repository: https://github.com/WICG/media-capabilities
File an issue: https://github.com/wicg/media-capabilities/issues/new
These tests are still very early. The specification is still WIP and they try to reflect as much as possible the current state of the specification. Please file issues if there are inconsistencies between the specification and the tests or if tests are obviously missing.