public Mediator(
     IDataRequestSubscriber dataRequestSubscriber,
     IApplicationHeartbeatService heartbeatService,
     ILogger <Mediator> logger)
 {
     this._dataRequestSubscriber =
         dataRequestSubscriber ?? throw new ArgumentNullException(nameof(dataRequestSubscriber));
     this._heartbeatService = heartbeatService ?? throw new ArgumentNullException(nameof(heartbeatService));
     this._logger           = logger ?? throw new ArgumentNullException(nameof(logger));
 }
 public void Setup()
 {
     this._logger                      = A.Fake <ILogger <Mediator> >();
     this._dataRequestService          = A.Fake <IDataRequestSubscriber>();
     this._applicationHeartbeatService = A.Fake <IApplicationHeartbeatService>();
 }