Heads up: I'm expecting a fair amount of tests to fail - the tests that use "fake" element mocks. I will fix them all.

So, tests worked as intended and I realized that style[x] =y and style.setProperty(x, y) are not equivalent in one important aspect. Style accessor accepts dashed and camel-case property names. I.e. both style['background-color'] and style['backgroundColor'] are ok. The setProperty('backgroundColor') however is not ok. In our code we by far prefer and use camel-case names. Thus this transition is harder to achieve.

Ah, good find.

Unfortunately have to close this per the issue described above.