Add more unit test.

MQTTnet.sln

@@ -7,11 +7,11 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MQTTnet", "Source\MQTTnet\M
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{B3F60ECB-45BA-4C66-8903-8BB89CA67998}"
 	ProjectSection(SolutionItems) = preProject
+		.github\workflows\ci.yml = .github\workflows\ci.yml
 		CODE-OF-CONDUCT.md = CODE-OF-CONDUCT.md
 		LICENSE = LICENSE
 		README.md = README.md
 		Source\ReleaseNotes.md = Source\ReleaseNotes.md
-		.github\workflows\ci.yml = .github\workflows\ci.yml
 	EndProjectSection
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MQTTnet.AspNetCore", "Source\MQTTnet.AspnetCore\MQTTnet.AspNetCore.csproj", "{F10C4060-F7EE-4A83-919F-FF723E72F94A}"
@@ -85,6 +85,4 @@ Global
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {07536672-5CBC-4BE3-ACE0-708A431A7894}
 	EndGlobalSection
-	GlobalSection(NestedProjects) = preSolution
-	EndGlobalSection
 EndGlobal

Source/MQTTnet.AspnetCore/Internal/MqttConnectionMiddleware.cs

@@ -49,7 +49,7 @@ public async Task InvokeAsync(ConnectionDelegate next, ConnectionContext connect
         }
     }
 
-    private static bool IsMqttRequest(ReadOnlySequence<byte> buffer)
+    public static bool IsMqttRequest(ReadOnlySequence<byte> buffer)
     {
         if (!buffer.IsEmpty)
         {

Source/MQTTnet.Tests/ASP/MqttConnectionMiddlewareTest.cs

@@ -0,0 +1,24 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using MQTTnet.AspNetCore;
+using System;
+using System.Buffers;
+
+namespace MQTTnet.Tests.ASP
+{
+    [TestClass]
+    public class MqttConnectionMiddlewareTest
+    {
+        [TestMethod]
+        public void IsMqttRequestTest()
+        {
+            var mqttv31Request = Convert.FromHexString("102800044d51545404c0003c0008636c69656e7469640008757365726e616d650008706173736f777264");
+            var mqttv50Request = Convert.FromHexString("102900044d51545405c0003c000008636c69656e7469640008757365726e616d650008706173736f777264");
+
+            var isMqttv31 = MqttConnectionMiddleware.IsMqttRequest(new ReadOnlySequence<byte>(mqttv31Request));
+            var isMqttv50 = MqttConnectionMiddleware.IsMqttRequest(new ReadOnlySequence<byte>(mqttv50Request));
+
+            Assert.IsTrue(isMqttv31);
+            Assert.IsTrue(isMqttv50);
+        }
+    }
+}