Testing exposed methods

The current test suite focuses on properties and attributes. That is only half of the DOM. You need to be able to also provide methods on your custom elements. Not having that ability automatically makes the APIs awkward (`instance.isOpen = true` _instead of_ `instance.open()` rather than _in addition to_).

The current version of test cases is not representative and is tailored towards frameworks, not developers using them. It's basically a lie what the reports say.