Improve Unit Tests.

Tests/MQTTnet.Core.Tests/MQTTv5/Client_Tests.cs

@@ -1,5 +1,4 @@
 using System.Collections.Generic;
-using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using MQTTnet.Client;
@@ -10,20 +9,16 @@ using MQTTnet.Client.Subscribing;
 using MQTTnet.Client.Unsubscribing;
 using MQTTnet.Formatter;
 using MQTTnet.Protocol;
-using MQTTnet.Server;
-using MQTTnet.Tests.Mockups;
 
 namespace MQTTnet.Tests.MQTTv5
 {
     [TestClass]
-    public sealed class Client_Tests
+    public sealed class Client_Tests : BaseTestClass
     {
-        public TestContext TestContext { get; set; }
-
         [TestMethod]
         public async Task Connect_With_New_Mqtt_Features()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer();
 
@@ -64,7 +59,7 @@ namespace MQTTnet.Tests.MQTTv5
         [TestMethod]
         public async Task Connect()
         {
-            using (var testEnvironment = new TestEnvironment())
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer();
                 await testEnvironment.ConnectClient(o => o.WithProtocolVersion(MqttProtocolVersion.V500).Build());
@@ -74,7 +69,7 @@ namespace MQTTnet.Tests.MQTTv5
         [TestMethod]
         public async Task Connect_And_Disconnect()
         {
-            using (var testEnvironment = new TestEnvironment())
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer();
 
@@ -86,7 +81,7 @@ namespace MQTTnet.Tests.MQTTv5
         [TestMethod]
         public async Task Subscribe()
         {
-            using (var testEnvironment = new TestEnvironment())
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer();
 
@@ -112,7 +107,7 @@ namespace MQTTnet.Tests.MQTTv5
         [TestMethod]
         public async Task Unsubscribe()
         {
-            using (var testEnvironment = new TestEnvironment())
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer();
 
@@ -130,7 +125,7 @@ namespace MQTTnet.Tests.MQTTv5
         [TestMethod]
         public async Task Publish_QoS_0()
         {
-            using (var testEnvironment = new TestEnvironment())
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer();
 
@@ -145,7 +140,7 @@ namespace MQTTnet.Tests.MQTTv5
         [TestMethod]
         public async Task Publish_QoS_1()
         {
-            using (var testEnvironment = new TestEnvironment())
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer();
 
@@ -160,7 +155,7 @@ namespace MQTTnet.Tests.MQTTv5
         [TestMethod]
         public async Task Publish_QoS_2()
         {
-            using (var testEnvironment = new TestEnvironment())
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer();
 
@@ -175,7 +170,7 @@ namespace MQTTnet.Tests.MQTTv5
         [TestMethod]
         public async Task Publish_With_Properties()
         {
-            using (var testEnvironment = new TestEnvironment())
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer();
 
@@ -204,7 +199,7 @@ namespace MQTTnet.Tests.MQTTv5
         [TestMethod]
         public async Task Subscribe_And_Publish()
         {
-            using (var testEnvironment = new TestEnvironment())
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer();
 
@@ -230,7 +225,7 @@ namespace MQTTnet.Tests.MQTTv5
                 await client1.DisconnectAsync();
 
                 Assert.AreEqual(1, receivedMessages.Count);
-                Assert.AreEqual("client1", receivedMessages[0].ClientId);
+                Assert.AreEqual("Subscribe_And_Publish_client1", receivedMessages[0].ClientId);
                 Assert.AreEqual("a", receivedMessages[0].ApplicationMessage.Topic);
                 Assert.AreEqual("b", receivedMessages[0].ApplicationMessage.ConvertPayloadToString());
             }
@@ -239,7 +234,7 @@ namespace MQTTnet.Tests.MQTTv5
         [TestMethod]
         public async Task Publish_And_Receive_New_Properties()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer();
 

Tests/MQTTnet.Core.Tests/Mockups/TestClientWrapper.cs

@@ -1,4 +1,5 @@
-using Microsoft.VisualStudio.TestTools.UnitTesting;
+using System;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
 using MQTTnet.Client;
 using MQTTnet.Client.Connecting;
 using MQTTnet.Client.Disconnecting;
@@ -17,7 +18,7 @@ namespace MQTTnet.Tests.Mockups
     {
         public TestClientWrapper(IMqttClient implementation, TestContext testContext)
         {
-            Implementation = implementation;
+            Implementation = implementation ?? throw new ArgumentNullException(nameof(implementation));
             TestContext = testContext;
         }
 
@@ -56,7 +57,7 @@ namespace MQTTnet.Tests.Mockups
                 var existingClientId = clientOptions.ClientId;
                 if (existingClientId != null && !existingClientId.StartsWith(TestContext.TestName))
                 {
-                    clientOptions.ClientId = TestContext.TestName + existingClientId;
+                    clientOptions.ClientId = TestContext.TestName + "_" + existingClientId;
                 }
             }
 

Tests/MQTTnet.Core.Tests/Server/General.cs

@@ -11,7 +11,6 @@ using MQTTnet.Client.Connecting;
 using MQTTnet.Client.Disconnecting;
 using MQTTnet.Client.Options;
 using MQTTnet.Client.Receiving;
-using MQTTnet.Client.Subscribing;
 using MQTTnet.Formatter;
 using MQTTnet.Protocol;
 using MQTTnet.Server;
@@ -20,10 +19,8 @@ using MQTTnet.Tests.Mockups;
 namespace MQTTnet.Tests.Server
 {
     [TestClass]
-    public sealed class General_Tests
+    public sealed class General_Tests : BaseTestClass
     {
-        public TestContext TestContext { get; set; }
-
         [TestMethod]
         [DataRow("", null)]
         [DataRow("", "")]
@@ -51,7 +48,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Use_Empty_Client_ID()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer();
 
@@ -77,8 +74,7 @@ namespace MQTTnet.Tests.Server
                 MqttQualityOfServiceLevel.AtMostOnce,
                 "A/B/C",
                 MqttQualityOfServiceLevel.AtMostOnce,
-                1,
-                TestContext);
+                1);
         }
 
         [TestMethod]
@@ -89,8 +85,7 @@ namespace MQTTnet.Tests.Server
                 MqttQualityOfServiceLevel.AtLeastOnce,
                 "A/B/C",
                 MqttQualityOfServiceLevel.AtLeastOnce,
-                1,
-                TestContext);
+                1);
         }
 
         [TestMethod]
@@ -101,14 +96,13 @@ namespace MQTTnet.Tests.Server
                 MqttQualityOfServiceLevel.ExactlyOnce,
                 "A/B/C",
                 MqttQualityOfServiceLevel.ExactlyOnce,
-                1,
-                TestContext);
+                1);
         }
 
         [TestMethod]
         public async Task Use_Clean_Session()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer();
 
@@ -122,7 +116,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Will_Message_Do_Not_Send_On_Clean_Disconnect()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 var receivedMessagesCount = 0;
 
@@ -148,7 +142,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Will_Message_Do_Not_Send_On_Takeover()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 var receivedMessagesCount = 0;
 
@@ -180,7 +174,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Will_Message_Send()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 var receivedMessagesCount = 0;
 
@@ -206,7 +200,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Publish_From_Server()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 var server = await testEnvironment.StartServer();
 
@@ -231,7 +225,7 @@ namespace MQTTnet.Tests.Server
         {
             var receivedMessagesCount = 0;
 
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer();
 
@@ -262,7 +256,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Session_Takeover()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer();
 
@@ -290,7 +284,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task No_Messages_If_No_Subscription()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer();
 
@@ -320,7 +314,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Set_Subscription_At_Server()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 var server = await testEnvironment.StartServer();
 
@@ -356,7 +350,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Shutdown_Disconnects_Clients_Gracefully()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 var server = await testEnvironment.StartServer(new MqttServerOptionsBuilder());
 
@@ -378,7 +372,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Handle_Clean_Disconnect()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 var server = await testEnvironment.StartServer(new MqttServerOptionsBuilder());
 
@@ -409,7 +403,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Client_Disconnect_Without_Errors()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 bool clientWasConnected;
 
@@ -440,7 +434,7 @@ namespace MQTTnet.Tests.Server
         {
             const int ClientCount = 50;
 
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 var server = await testEnvironment.StartServer();
 
@@ -494,7 +488,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Intercept_Application_Message()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer(
                     new MqttServerOptionsBuilder().WithApplicationMessageInterceptor(
@@ -517,7 +511,7 @@ namespace MQTTnet.Tests.Server
         {
             var serverStorage = new TestServerStorage();
 
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer(new MqttServerOptionsBuilder().WithStorage(serverStorage));
 
@@ -534,7 +528,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Publish_After_Client_Connects()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 var server = await testEnvironment.StartServer();
                 server.UseClientConnectedHandler(async e => { await server.PublishAsync("/test/1", "true", MqttQualityOfServiceLevel.ExactlyOnce, false); });
@@ -564,7 +558,7 @@ namespace MQTTnet.Tests.Server
                 context.ApplicationMessage.Payload = Encoding.ASCII.GetBytes("extended");
             }
 
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer(new MqttServerOptionsBuilder().WithApplicationMessageInterceptor(Interceptor));
 
@@ -587,7 +581,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Send_Long_Body()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 const int PayloadSizeInMB = 30;
                 const int CharCount = PayloadSizeInMB * 1024 * 1024;
@@ -630,7 +624,7 @@ namespace MQTTnet.Tests.Server
         {
             var serverOptions = new MqttServerOptionsBuilder().WithConnectionValidator(context => { context.ReasonCode = MqttConnectReasonCode.NotAuthorized; });
 
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 testEnvironment.IgnoreClientLogErrors = true;
 
@@ -659,7 +653,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Same_Client_Id_Refuse_Connection()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 testEnvironment.IgnoreClientLogErrors = true;
 
@@ -747,7 +741,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Same_Client_Id_Connect_Disconnect_Event_Order()
         {
-            using (var testEnvironment = new TestEnvironment())
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 var server = await testEnvironment.StartServer(new MqttServerOptionsBuilder());
 
@@ -832,7 +826,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Remove_Session()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 var server = await testEnvironment.StartServer(new MqttServerOptionsBuilder());
 
@@ -851,7 +845,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Stop_And_Restart()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 testEnvironment.IgnoreClientLogErrors = true;
 
@@ -877,7 +871,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Do_Not_Send_Retained_Messages_For_Denied_Subscription()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer(new MqttServerOptionsBuilder().WithSubscriptionInterceptor(c =>
                 {
@@ -921,7 +915,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Collect_Messages_In_Disconnected_Session()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 var server = await testEnvironment.StartServer(new MqttServerOptionsBuilder().WithPersistentSessions());
 
@@ -952,15 +946,14 @@ namespace MQTTnet.Tests.Server
             }
         }
 
-        static async Task TestPublishAsync(
+        async Task TestPublishAsync(
             string topic,
             MqttQualityOfServiceLevel qualityOfServiceLevel,
             string topicFilter,
             MqttQualityOfServiceLevel filterQualityOfServiceLevel,
-            int expectedReceivedMessagesCount,
-            TestContext testContext)
+            int expectedReceivedMessagesCount)
         {
-            using (var testEnvironment = new TestEnvironment(testContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 var receivedMessagesCount = 0;
 
@@ -985,7 +978,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Intercept_Undelivered()
         {
-            using (var testEnvironment = new TestEnvironment())
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 var undeliverd = string.Empty;
 
@@ -1009,7 +1002,7 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Intercept_ClientMessageQueue()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer(new MqttServerOptionsBuilder()
                     .WithClientMessageQueueInterceptor(c => c.ApplicationMessage.Topic = "a"));
@@ -1047,7 +1040,7 @@ namespace MQTTnet.Tests.Server
         {
             const string topic = "a";
 
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 await testEnvironment.StartServer(new MqttServerOptionsBuilder()
                     .WithClientMessageQueueInterceptor(c => { })); // Interceptor does nothing but has to be present.

Tests/MQTTnet.Core.Tests/Server/Session_Tests.cs

@@ -1,42 +1,47 @@
-using System.Linq;
+using System;
+using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using MQTTnet.Client;
 using MQTTnet.Client.Options;
 using MQTTnet.Client.Subscribing;
+using MQTTnet.Protocol;
 using MQTTnet.Server;
 using MQTTnet.Tests.Mockups;
 
 namespace MQTTnet.Tests.Server
 {
     [TestClass]
-    public class Session_Tests
-    {
-        public TestContext TestContext { get; set; }
-
+    public sealed class Session_Tests : BaseTestClass
+    { 
         [TestMethod]
         public async Task Set_Session_Item()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 var serverOptions = new MqttServerOptionsBuilder()
-                    .WithConnectionValidator(delegate (MqttConnectionValidatorContext context)
+                    .WithConnectionValidator(delegate(MqttConnectionValidatorContext context)
                     {
                         // Don't validate anything. Just set some session items.
                         context.SessionItems["can_subscribe_x"] = true;
                         context.SessionItems["default_payload"] = "Hello World";
                     })
-                    .WithSubscriptionInterceptor(delegate (MqttSubscriptionInterceptorContext context)
+                    .WithSubscriptionInterceptor(delegate(MqttSubscriptionInterceptorContext context)
                     {
                         if (context.TopicFilter.Topic == "x")
                         {
-                            context.AcceptSubscription = context.SessionItems["can_subscribe_x"] as bool? == true;
+                            if (context.SessionItems["can_subscribe_x"] as bool? == false)
+                            {
+                                context.ReasonCode = MqttSubscribeReasonCode.ImplementationSpecificError;
+                            }
                         }
                     })
-                    .WithApplicationMessageInterceptor(delegate (MqttApplicationMessageInterceptorContext context)
+                    .WithApplicationMessageInterceptor(delegate(MqttApplicationMessageInterceptorContext context)
                     {
-                        context.ApplicationMessage.Payload = Encoding.UTF8.GetBytes(context.SessionItems["default_payload"] as string);
+                        context.ApplicationMessage.Payload =
+                            Encoding.UTF8.GetBytes(
+                                context.SessionItems["default_payload"] as string ?? String.Empty);
                     });
 
                 await testEnvironment.StartServer(serverOptions);
@@ -44,7 +49,7 @@ namespace MQTTnet.Tests.Server
                 string receivedPayload = null;
 
                 var client = await testEnvironment.ConnectClient();
-                client.UseApplicationMessageReceivedHandler(delegate (MqttApplicationMessageReceivedEventArgs args)
+                client.UseApplicationMessageReceivedHandler(delegate(MqttApplicationMessageReceivedEventArgs args)
                 {
                     receivedPayload = args.ApplicationMessage.ConvertPayloadToString();
                 });
@@ -65,10 +70,10 @@ namespace MQTTnet.Tests.Server
         [TestMethod]
         public async Task Get_Session_Items_In_Status()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 var serverOptions = new MqttServerOptionsBuilder()
-                    .WithConnectionValidator(delegate (MqttConnectionValidatorContext context)
+                    .WithConnectionValidator(delegate(MqttConnectionValidatorContext context)
                     {
                         // Don't validate anything. Just set some session items.
                         context.SessionItems["can_subscribe_x"] = true;
@@ -77,7 +82,7 @@ namespace MQTTnet.Tests.Server
 
                 await testEnvironment.StartServer(serverOptions);
 
-                var client = await testEnvironment.ConnectClient();
+                await testEnvironment.ConnectClient();
 
                 var sessionStatus = await testEnvironment.Server.GetSessionStatusAsync();
                 var session = sessionStatus.First();
@@ -86,11 +91,10 @@ namespace MQTTnet.Tests.Server
             }
         }
 
-
         [TestMethod]
         public async Task Manage_Session_MaxParallel()
         {
-            using (var testEnvironment = new TestEnvironment(TestContext))
+            using (var testEnvironment = CreateTestEnvironment())
             {
                 testEnvironment.IgnoreClientLogErrors = true;
                 var serverOptions = new MqttServerOptionsBuilder();
@@ -106,6 +110,61 @@ namespace MQTTnet.Tests.Server
                 Assert.AreEqual(1, connectedClients.Count);
             }
         }
+        
+        [TestMethod]
+        public async Task Fire_Deleted_Event()
+        {
+            using (var testEnvironment = CreateTestEnvironment())
+            {
+                // Arrange client and server.
+                var server = await testEnvironment.StartServer(o => o.WithPersistentSessions(false));
+                var client = await testEnvironment.ConnectClient();
+
+                // Arrange session status tracking.
+                var status = await server.GetSessionStatusAsync();
+                var clientStatus = status[0];
+
+                var deletedEventFired = false;
+                clientStatus.Deleted += (_, __) =>
+                {
+                    deletedEventFired = true;
+                };
+                
+                // Act: Disconnect the client -> Event must be fired.
+                await client.DisconnectAsync();
+
+                await LongTestDelay();
+                
+                // Assert that the event was fired properly.
+                Assert.IsTrue(deletedEventFired);
+            }
+        }
+        
+        [TestMethod]
+        public async Task Inject_Application_Message()
+        {
+            using (var testEnvironment = CreateTestEnvironment())
+            {
+                // Arrange client and server.
+                var server = await testEnvironment.StartServer();
+                var client = await testEnvironment.ConnectClient();
+                var messageReceivedHandler = testEnvironment.CreateApplicationMessageHandler(client);
+                
+                // Arrange session status tracking.
+                var status = await server.GetSessionStatusAsync();
+                var clientStatus = status[0];
+
+                // Act: Inject the application message.
+                await clientStatus.EnqueueApplicationMessageAsync(new MqttApplicationMessageBuilder()
+                    .WithTopic("injected_one").Build());
+
+                await LongTestDelay();
+                
+                // Assert 
+                Assert.AreEqual(1, messageReceivedHandler.ReceivedApplicationMessages.Count);
+                Assert.AreEqual("injected_one", messageReceivedHandler.ReceivedApplicationMessages[0].Topic);
+            }
+        }
 
         async Task<IMqttClient> TryConnect(TestEnvironment testEnvironment, MqttClientOptionsBuilder options)
         {
@@ -113,10 +172,10 @@ namespace MQTTnet.Tests.Server
             {
                 return await testEnvironment.ConnectClient(options);
             }
-            catch (System.Exception)
+            catch
             {
                 return null;
             }
         }
     }
-}
+}