public void When_TickProvided_Then_MarketListenerReceiveTickEvent()
        {
            // setup
            var moq = new Mock <IMarketListener>();

            market.Subscribe(moq.Object);

            // when tick provided
            var tick = Tick.ForNow(100, 99);

            tickProvider.Raise(m => m.Tick += null, new TickEventArgs(tick));

            // then market listener should receive tick
            moq.Verify(m => m.OnTick(It.IsAny <Tick>()), Times.Once);
        }