[0.74] Prevent race condition in ConnectSucceeds WS unit test (#14408)

* Prevent race condition in ConnectSucceeds WS unit test (#14405)

* Prevent race condition in ConnectSucceeds

* Change files

* Remove change file

* Change files

Author: JunielKatarn

change/react-native-windows-58317a4c-c02e-4a5b-8cba-ed78a9e4fa26.json

@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Prevent race condition in ConnectSucceeds WS unit test (#14405)",
+  "packageName": "react-native-windows",
+  "email": "julio.rocha@microsoft.com",
+  "dependentChangeType": "patch"
+}

vnext/Desktop.UnitTests/WinRTWebSocketResourceUnitTest.cpp

@@ -55,19 +55,21 @@ TEST_CLASS (WinRTWebSocketResourceUnitTest) {
     auto imws{winrt::make<MockMessageWebSocket>()};
 
     // Set up mocks
+    auto callingQueue = Mso::DispatchQueue::MakeSerialQueue();
     auto mws{imws.as<MockMessageWebSocket>()};
     // TODO: Mock Control()
     mws->Mocks.ConnectAsync = [](const Uri &) -> IAsyncAction { return DoNothingAsync(); };
 
     // Test APIs
-    auto rc = make_shared<WinRTWebSocketResource2>(
-        std::move(imws), MockDataWriter{}, CertExceptions{}, Mso::DispatchQueue::MakeSerialQueue());
+    auto rc = make_shared<WinRTWebSocketResource2>(std::move(imws), MockDataWriter{}, CertExceptions{}, callingQueue);
     rc->SetOnConnect([&connected]() { connected = true; });
     rc->SetOnError([&errorMessage](Error &&error) { errorMessage = error.Message; });
 
     rc->Connect(testUrl, {}, {});
     rc->Close(CloseCode::Normal, {});
 
+    callingQueue.AwaitTermination();
+
     Assert::AreEqual({}, errorMessage);
     Assert::IsTrue(connected);
   }