Description
I measured the coverage of the DOM Events test suite against the standard and there seems to be a few coverage gaps. I list three scenarios below:
Scenario 1: Dispatch with optional flags
There seems to be no test calling the dispatchEvent function with the optional flags legacyTargetOverride and legacyOutputDidListenersThrow.
Additional test: calling dispatchEvent with optional flags activated and check whether handler is still triggered.
Scenario 2: Activation behaviour
Another potential scenario to cover is activation behaviour, which is triggered, for instance, if we call dispatchEvent on an element of type input.
Additional test: one could check if certain properties hold for the dispatch triggering activation behaviour, such as the event phase is set to NONE during the execution of a handler.
Scenario 3: Slottable feature
It could be interesting to write tests using the HTMLSlotElement.
Additional test: one could perhaps test if creating a slot on an input element and dispatching an event on the input element by calling dispatchEvent would trigger activation behaviour.
I appreciate any feedback regarding these scenarios. If necessary, I can submit additional tests via pull requests to improve the test suite coverage.