FYI @annevk @Sebmaster @jasnell. I managed to cobble this together: - [URL state machine coverage report](https://dl.dropboxusercontent.com/u/20140634/url-spec-coverage/lib/url-state-machine.js.html): ~99% - [URL object coverage report](https://dl.dropboxusercontent.com/u/20140634/url-spec-coverage/lib/URL-impl.js.html): ~94% Areas of lacking coverage are: - some origin serialization stuff (some purposefully untested) - The href setter - One early-return case in the hash setter - One "else" branch in IPv4 parsing