function fakeIncomingMessage(message, bus, senderId) {
    const serialized = CastUtils.serialize(message);
    const messageEvent = {
      senderId: senderId,
      data: serialized,
    };
    bus.onMessage(messageEvent);
  }
@param {*} message
@param {!cast.receiver.CastMessageBus} bus
@param {string=} senderId