Add extension methods.

Tests/MQTTnet.Core.Tests/Mockups/TestEnvironment.cs

@@ -21,7 +21,7 @@ namespace MQTTnet.Tests.Mockups
 
         private readonly List<Exception> _exceptions = new List<Exception>();
 
-        private IMqttServer _server;
+        public IMqttServer Server { get; private set; }
 
         public bool IgnoreClientLogErrors { get; set; }
 
@@ -72,15 +72,15 @@ namespace MQTTnet.Tests.Mockups
 
         public async Task<IMqttServer> StartServerAsync(MqttServerOptionsBuilder options)
         {
-            if (_server != null)
+            if (Server != null)
             {
                 throw new InvalidOperationException("Server already started.");
             }
 
-            _server = _mqttFactory.CreateMqttServer(_serverLogger);
-            await _server.StartAsync(options.WithDefaultEndpointPort(ServerPort).Build());
+            Server = _mqttFactory.CreateMqttServer(_serverLogger);
+            await Server.StartAsync(options.WithDefaultEndpointPort(ServerPort).Build());
 
-            return _server;
+            return Server;
         }
 
         public Task<IMqttClient> ConnectClientAsync()
@@ -122,7 +122,7 @@ namespace MQTTnet.Tests.Mockups
                 mqttClient?.Dispose();
             }
 
-            _server?.StopAsync().GetAwaiter().GetResult();
+            Server?.StopAsync().GetAwaiter().GetResult();
 
             ThrowIfLogErrors();
 

Tests/MQTTnet.Core.Tests/MqttClient_Tests.cs

@@ -295,5 +295,49 @@ namespace MQTTnet.Tests
                 Assert.IsFalse(client.IsConnected);
             }
         }
+
+        [TestMethod]
+        public async Task Frequent_Connects()
+        {
+            using (var testEnvironment = new TestEnvironment())
+            {
+                await testEnvironment.StartServerAsync();
+
+                var clients = new List<IMqttClient>();
+                for (var i = 0; i < 100; i++)
+                {
+                    clients.Add(await testEnvironment.ConnectClientAsync(new MqttClientOptionsBuilder().WithClientId("a")));
+                }
+
+                var clientStatus = await testEnvironment.Server.GetClientStatusAsync();
+                var sessionStatus = await testEnvironment.Server.GetSessionStatusAsync();
+
+                for (var i = 0; i < 98; i++)
+                {
+                    Assert.IsFalse(clients[i].IsConnected);
+                }
+                
+                Assert.IsTrue(clients[99].IsConnected);
+
+                Assert.AreEqual(1, clientStatus.Count);
+                Assert.AreEqual(1, sessionStatus.Count);
+
+                var receiveClient = clients[99];
+                object receivedPayload = null;
+                receiveClient.UseApplicationMessageReceivedHandler(e =>
+                {
+                    receivedPayload = e.ApplicationMessage.ConvertPayloadToString();
+                });
+
+                await receiveClient.SubscribeAsync("x");
+
+                var sendClient = await testEnvironment.ConnectClientAsync();
+                await sendClient.PublishAsync("x", "1");
+
+                await Task.Delay(100);
+
+                Assert.AreEqual("1", receivedPayload);
+            }
+        }
     }
 }