Fix runtime review findings

clients/dotnet/MxGateway.Client.Tests/FakeGalaxyRepositoryTransport.cs

@@ -21,6 +21,8 @@ internal sealed class FakeGalaxyRepositoryTransport(MxGatewayClientOptions optio
 
     public DiscoverHierarchyReply DiscoverHierarchyReply { get; set; } = new();
 
+    public Queue<DiscoverHierarchyReply> DiscoverHierarchyReplies { get; } = new();
+
     public Queue<Exception> TestConnectionExceptions { get; } = new();
 
     public Queue<Exception> GetLastDeployTimeExceptions { get; } = new();
@@ -63,7 +65,10 @@ internal sealed class FakeGalaxyRepositoryTransport(MxGatewayClientOptions optio
             throw exception;
         }
 
-        return Task.FromResult(DiscoverHierarchyReply);
+        return Task.FromResult(
+            DiscoverHierarchyReplies.TryDequeue(out DiscoverHierarchyReply? reply)
+                ? reply
+                : DiscoverHierarchyReply);
     }
 
     public List<(WatchDeployEventsRequest Request, CallOptions CallOptions)> WatchDeployEventsCalls { get; } = [];