public void Initialize()
 {
     serviceClient       = new Mock <IEventServiceClient>();
     subscriptionCache   = new Mock <IEventSubscriptionCache>();
     subscriptionService = new Mock <ISubscriptionService>();
     sink = new AppHostEventSink
     {
         ServiceClient       = serviceClient.Object,
         SubscriptionCache   = subscriptionCache.Object,
         SubscriptionService = subscriptionService.Object
     };
 }