How to add tests

Go to tests.js. Follow the current structure. Please only add tests from specs that are reasonably stable. They don't have to be a CR, just not too much in Flux.

Don't add specs when there are NO implementations of ANYTHING in the spec.
Don't add tests that already exist, just with different values. E.g. if calc(1px + 2px) is a testcase, adding calc(2px + 2px) won't help.