     verifySwitchingAggressively src, expectedEvents
 
 @expectPropertyEvents = (src, expectedEvents, {unstable, extraCheck} = {}) ->
-  expect(expectedEvents.length > 0).to.deep.equal(true)
+  expect(expectedEvents.length > 0).to.deep.equal(true, "at least one expected event is specified")
   verifyPSingleSubscriber src, expectedEvents, extraCheck
   verifyPLateEval src, expectedEvents
   if not unstable

    events = []
    before -> 
      src = srcF()
      expect(src instanceof Bacon.EventStream).to.equal(true)
    before (done) ->
      collectF(src, events, done)
    it "outputs expected value in order", ->

      if event.isEnd()
        done()
      else
        expect(event instanceof Bacon.Initial).to.deep.equal(false, "no Initial events")
        events.push(toValue(event))

# get each event with new subscriber
