this is fishy: with TestTimeFactor of 1 this will wait for more than 1 second, which will fail on slow systems due to the `within` constraint.

Well, actually the above is what _should_ happen :-( but instead TestKit just does not check the bound if the last action was a NoMsg, so the above is just a complicated way of saying

    expectTransition(1.second, Idle, Active)
    expectNoMsg(expectNoMsgTimeout)

(with a presumed change to the `expectTransition` method).