assert_equals: expected "0px" but got "50px"
Instead of setTimeout and step_timeout that are deprecated (and do cause trouble) may I suggest relying on animation-delay to be able to check the correct values in a simple requestAnimationFrame from the get go?
@FremyCompany Is the latest commit what you meant? This seems to work when the tests pass, but when they fail I see an uncaught exception as well as the testharness failure.