Check for Event Parameters

In order to check event parameters and the fact that event has been fired you can use the following example:

//Get event from aura object (you have to add it while calling auraFactory)
const showEvent = $A.get('e.Framework:ShowComponentEvent');

//Check event parameters (yes, you can use component.get('v.var') as usual in your tests)
expect(showEvent.getParams()).to.eql({
    componentName: 'c:EventRegistrationTicketSelection',
    componentParams: {
        attendeeObj : component.get('v.attendeeObj'),
        usr : component.get('v.usr'),
        eventObj : component.get('v.eventObj'),
        siteObj : component.get('v.siteObj'),
        storeObj : component.get('v.storeObj'),
        salesOrderObj : component.get('v.salesOrderObj'),
        secondaryCompName : 'c:EventRegistrationTicketSelection',
        identifier : 'EventRegistrationWrapper',
        linesByTicket: component.get('v.linesByTicket'),
        showRegisterButton: false
 }
})

//Check that event has been fired
expect(showEvent.fire).to.have.been.called;