Even bus tester improvements

[brendt]

• It should be possible to make assertions on dispatched events even when the event bus was not faked.
• assertDispatched has a default count of null, causing the method to succeed by default when no events were dispatched fix(eventbus): change dispatched assertion from not null to not empty #1709

[WendellAdriel]

I created #1530 as a proposal to fix this