Add test

Author: simon-lemay-unity

com.unity.netcode.gameobjects/Tests/Runtime/Transports/UnityTransportTests.cs

@@ -483,5 +483,22 @@ public IEnumerator DoesNotActAfterShutdown([Values] AfterShutdownAction afterShu
                 yield return EnsureNoNetworkEvent(m_Client1Events);
             }
         }
+
+        [UnityTest]
+        public IEnumerator DoesNotAttemptToSendOnInvalidConnections()
+        {
+            InitializeTransport(out m_Server, out m_ServerEvents);
+            InitializeTransport(out m_Client1, out m_Client1Events);
+
+            m_Server.StartServer();
+            m_Client1.StartClient();
+
+            yield return WaitForNetworkEvent(NetworkEvent.Connect, m_Client1Events);
+
+            var data = new ArraySegment<byte>(new byte[42]);
+            m_Server.Send(m_Client1.ServerClientId, data, NetworkDelivery.Reliable);
+
+            yield return EnsureNoNetworkEvent(m_Client1Events);
+        }
     }
 }