Testing directive

We still have a lot of specs to write...

This PR is singled out to document an efficient way on how to test our directives.

The `unusedTokenHighlighter`'s spec file contains comments on how to do this and should serve as a blueprint for the future.
it might be obvious, but it could helpful to add a comment here that the purpose of this test is to verify that the uth-check-property is actually read, and that the code doesn't default to only looking at the head.id state (assuming that is the point)