handled

Wouldn't for .. of be functionally identical (And slightly easier to read)?

Id, class, and element are not a kind of "decimal" or "powers of ten", where 100 classes = 1 Id. A single ID always overrides a class, no matter how many classes there are.

though, fun fact, browsers did not implement this correctly: http://www.thecssninja.com/css/extreme-specificity

It's implementation, not part of standard. In this kata, you should not count on this number.

if #id = 100 and .class = 10, then 257 class should be more priorisized than an #id.

Is this test wrong?

At this point, only moderators can change the test cases. Sorry :/.

Great tests! Good work on this Kata by the tests.

This Kata is buggy! If you return just an array of string it will be pass!