test(comm): de-race StreamRelay null-map + SiteConnectionUp gauge under load (#288)

tests/ZB.MOM.WW.ScadaBridge.Communication.Tests/Grpc/SiteStreamGrpcServerTests.cs

@@ -386,15 +386,23 @@ public class SiteStreamGrpcServerTests : TestKit
         // While the stream is up the gauge is one above whatever baseline other
         // (possibly parallel) tests left behind — read relative so the assertion
         // is robust to test interleaving on the process-wide static counter.
-        Assert.Equal(baseline + 1, ReadGauge());
+        //
+        // SiteConnectionOpened() runs AFTER the _activeStreams insertion that
+        // WaitForConditionAsync(ActiveStreamCount == 1) keys off (see
+        // SiteStreamGrpcServer.SubscribeInstance), so a one-shot ReadGauge() here
+        // can race the increment under full-suite CPU oversubscription. Poll the
+        // gauge with a generous timeout until it reaches baseline + 1.
+        AwaitAssert(() => Assert.Equal(baseline + 1, ReadGauge()), TimeSpan.FromSeconds(5));
 
         cts.Cancel();
         await streamTask;
         await WaitForConditionAsync(() => server.ActiveStreamCount == 0);
 
         // After the cancel path runs the finally, the gauge is balanced back to
-        // the baseline — no leaked "up" count.
-        Assert.Equal(baseline, ReadGauge());
+        // the baseline — no leaked "up" count. Poll here too: the gauge decrement
+        // and the stream-count drop are independent observations, so under load
+        // give the finally's SiteConnectionClosed() time to land.
+        AwaitAssert(() => Assert.Equal(baseline, ReadGauge()), TimeSpan.FromSeconds(5));
     }
 
     [Fact]