diff --git a/.github/workflows/sonarcloud.yml b/.github/workflows/sonarcloud.yml
index e784069..49217c6 100644
--- a/.github/workflows/sonarcloud.yml
+++ b/.github/workflows/sonarcloud.yml
@@ -37,6 +37,8 @@ on:
 
 permissions:
   pull-requests: read # allows SonarCloud to decorate PRs with analysis results
+  contents: read
+
 
 jobs:
   sonar-check:
@@ -56,8 +58,8 @@ jobs:
           dotnet tool install --global dotnet-sonarscanner
           echo "$env:USERPROFILE\.dotnet\tools" >> $env:GITHUB_PATH
           dotnet sonarscanner begin `
-          /k:"ppanchen_NetSdrClient" `
-          /o:"ppanchen" `
+          /k:"slavik22_ReengineeringCourse" `
+          /o:"slavik22" `
           /d:sonar.token="${{ secrets.SONAR_TOKEN }}" `
           /d:sonar.cs.opencover.reportsPaths="**/coverage.xml" `
           /d:sonar.cpd.cs.minimumTokens=40 `
@@ -70,13 +72,13 @@ jobs:
         run: dotnet restore NetSdrClient.sln
       - name: Build
         run: dotnet build NetSdrClient.sln -c Release --no-restore
-      #- name: Tests with coverage (OpenCover)
-      #  run: |
-      #    dotnet test NetSdrClientAppTests/NetSdrClientAppTests.csproj -c Release --no-build `
-      #      /p:CollectCoverage=true `
-      #      /p:CoverletOutput=TestResults/coverage.xml `
-      #      /p:CoverletOutputFormat=opencover
-      #  shell: pwsh
+      - name: Tests with coverage (OpenCover)
+        run: |
+          dotnet test NetSdrClientAppTests/NetSdrClientAppTests.csproj -c Release --no-build `
+            /p:CollectCoverage=true `
+            /p:CoverletOutput=TestResults/coverage.xml `
+            /p:CoverletOutputFormat=opencover
+        shell: pwsh
       # 3) END: SonarScanner
       - name: SonarScanner End
         run: dotnet sonarscanner end /d:sonar.token="${{ secrets.SONAR_TOKEN }}"
diff --git a/NetSdrClientApp/Messages/NetSdrMessageHelper.cs b/NetSdrClientApp/Messages/NetSdrMessageHelper.cs
index 0d69b4d..b0ec931 100644
--- a/NetSdrClientApp/Messages/NetSdrMessageHelper.cs
+++ b/NetSdrClientApp/Messages/NetSdrMessageHelper.cs
@@ -1,10 +1,4 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Reflection.PortableExecutable;
-using System.Text;
-using System.Threading.Tasks;
-
+
 namespace NetSdrClientApp.Messages
 {
     //TODO: analyze possible use of [StructLayout] for better performance and readability 
@@ -83,7 +77,7 @@ public static bool TranslateMessage(byte[] msg, out MsgTypes type, out ControlIt
                 msgEnumarable = msgEnumarable.Skip(_msgControlItemLength);
                 msgLength -= _msgControlItemLength;
 
-                if (Enum.IsDefined(typeof(ControlItemCodes), value))
+                if (Enum.IsDefined(typeof(ControlItemCodes), (int)value))
                 {
                     itemCode = (ControlItemCodes)value;
                 }
@@ -111,7 +105,7 @@ public static IEnumerable<int> GetSamples(ushort sampleSize, byte[] body)
             sampleSize /= 8; //to bytes
             if (sampleSize  > 4)
             {
-                throw new ArgumentOutOfRangeException();
+                throw new ArgumentOutOfRangeException(nameof(sampleSize), sampleSize, "Sample size must be 8, 16, 24, or 32 bits.");
             }
 
             var bodyEnumerable = body as IEnumerable<byte>;
diff --git a/NetSdrClientApp/NetSdrClient.cs b/NetSdrClientApp/NetSdrClient.cs
index b0a7c05..1b9a04f 100644
--- a/NetSdrClientApp/NetSdrClient.cs
+++ b/NetSdrClientApp/NetSdrClient.cs
@@ -1,21 +1,13 @@
 using NetSdrClientApp.Messages;
 using NetSdrClientApp.Networking;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading;
-using System.Threading.Channels;
-using System.Threading.Tasks;
 using static NetSdrClientApp.Messages.NetSdrMessageHelper;
-using static System.Runtime.InteropServices.JavaScript.JSType;
 
 namespace NetSdrClientApp
 {
     public class NetSdrClient
     {
-        private ITcpClient _tcpClient;
-        private IUdpClient _udpClient;
+        private readonly ITcpClient _tcpClient;
+        private readonly IUdpClient _udpClient;
 
         public bool IQStarted { get; set; }
 
@@ -66,7 +58,7 @@ public async Task StartIQAsync()
                 return;
             }
 
-;           var iqDataMode = (byte)0x80;
+            var iqDataMode = (byte)0x80;
             var start = (byte)0x02;
             var fifo16bitCaptureMode = (byte)0x01;
             var n = (byte)1;
@@ -116,7 +108,7 @@ public async Task ChangeFrequencyAsync(long hz, int channel)
 
         private void _udpClient_MessageReceived(object? sender, byte[] e)
         {
-            NetSdrMessageHelper.TranslateMessage(e, out MsgTypes type, out ControlItemCodes code, out ushort sequenceNum, out byte[] body);
+            NetSdrMessageHelper.TranslateMessage(e, out _, out _, out _, out byte[] body);
             var samples = NetSdrMessageHelper.GetSamples(16, body);
 
             Console.WriteLine($"Samples recieved: " + body.Select(b => Convert.ToString(b, toBase: 16)).Aggregate((l, r) => $"{l} {r}"));
@@ -131,9 +123,9 @@ private void _udpClient_MessageReceived(object? sender, byte[] e)
             }
         }
 
-        private TaskCompletionSource<byte[]> responseTaskSource;
+        private TaskCompletionSource<byte[]>? responseTaskSource;
 
-        private async Task<byte[]> SendTcpRequest(byte[] msg)
+        private async Task<byte[]?> SendTcpRequest(byte[] msg)
         {
             if (!_tcpClient.Connected)
             {
diff --git a/NetSdrClientApp/Networking/ITcpClient.cs b/NetSdrClientApp/Networking/ITcpClient.cs
index 3470b5d..e779e95 100644
--- a/NetSdrClientApp/Networking/ITcpClient.cs
+++ b/NetSdrClientApp/Networking/ITcpClient.cs
@@ -1,11 +1,4 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-using static System.Runtime.InteropServices.JavaScript.JSType;
-
-namespace NetSdrClientApp.Networking
+namespace NetSdrClientApp.Networking
 {
     public interface ITcpClient
     {
diff --git a/NetSdrClientApp/Networking/IUdpClient.cs b/NetSdrClientApp/Networking/IUdpClient.cs
index 1b9f931..053262b 100644
--- a/NetSdrClientApp/Networking/IUdpClient.cs
+++ b/NetSdrClientApp/Networking/IUdpClient.cs
@@ -1,10 +1,13 @@
-
-public interface IUdpClient
+
+namespace NetSdrClientApp.Networking
 {
-    event EventHandler<byte[]>? MessageReceived;
+    public interface IUdpClient
+    {
+        event EventHandler<byte[]>? MessageReceived;
 
-    Task StartListeningAsync();
+        Task StartListeningAsync();
 
-    void StopListening();
-    void Exit();
-}
\ No newline at end of file
+        void StopListening();
+        void Exit();
+    }
+}
diff --git a/NetSdrClientApp/Networking/TcpClientWrapper.cs b/NetSdrClientApp/Networking/TcpClientWrapper.cs
index 1f37e2e..ade0102 100644
--- a/NetSdrClientApp/Networking/TcpClientWrapper.cs
+++ b/NetSdrClientApp/Networking/TcpClientWrapper.cs
@@ -1,22 +1,15 @@
-using System;
-using System.Collections.Generic;
-using System.IO;
-using System.Linq;
-using System.Net.Http;
-using System.Net.Sockets;
+using System.Net.Sockets;
 using System.Text;
-using System.Threading;
-using System.Threading.Tasks;
 
 namespace NetSdrClientApp.Networking
 {
     public class TcpClientWrapper : ITcpClient
     {
-        private string _host;
-        private int _port;
+        private readonly string _host;
+        private readonly int _port;
         private TcpClient? _tcpClient;
         private NetworkStream? _stream;
-        private CancellationTokenSource _cts;
+        private CancellationTokenSource? _cts;
 
         public bool Connected => _tcpClient != null && _tcpClient.Connected && _stream != null;
 
@@ -57,6 +50,7 @@ public void Disconnect()
             if (Connected)
             {
                 _cts?.Cancel();
+                _cts?.Dispose();
                 _stream?.Close();
                 _tcpClient?.Close();
 
@@ -71,22 +65,12 @@ public void Disconnect()
             }
         }
 
-        public async Task SendMessageAsync(byte[] data)
-        {
-            if (Connected && _stream != null && _stream.CanWrite)
-            {
-                Console.WriteLine($"Message sent: " + data.Select(b => Convert.ToString(b, toBase: 16)).Aggregate((l, r) => $"{l} {r}"));
-                await _stream.WriteAsync(data, 0, data.Length);
-            }
-            else
-            {
-                throw new InvalidOperationException("Not connected to a server.");
-            }
-        }
+        public Task SendMessageAsync(byte[] data) => SendBytesAsync(data);
+
+        public Task SendMessageAsync(string str) => SendBytesAsync(Encoding.UTF8.GetBytes(str));
 
-        public async Task SendMessageAsync(string str)
+        private async Task SendBytesAsync(byte[] data)
         {
-            var data = Encoding.UTF8.GetBytes(str);
             if (Connected && _stream != null && _stream.CanWrite)
             {
                 Console.WriteLine($"Message sent: " + data.Select(b => Convert.ToString(b, toBase: 16)).Aggregate((l, r) => $"{l} {r}"));
@@ -117,7 +101,7 @@ private async Task StartListeningAsync()
                         }
                     }
                 }
-                catch (OperationCanceledException ex)
+                catch (OperationCanceledException)
                 {
                     //empty
                 }
diff --git a/NetSdrClientApp/Networking/UdpClientWrapper.cs b/NetSdrClientApp/Networking/UdpClientWrapper.cs
index 31e0b79..8201c46 100644
--- a/NetSdrClientApp/Networking/UdpClientWrapper.cs
+++ b/NetSdrClientApp/Networking/UdpClientWrapper.cs
@@ -1,85 +1,73 @@
-using System;
 using System.Net;
 using System.Net.Sockets;
 using System.Security.Cryptography;
 using System.Text;
-using System.Threading;
-using System.Threading.Tasks;
 
-public class UdpClientWrapper : IUdpClient
+namespace NetSdrClientApp.Networking
 {
-    private readonly IPEndPoint _localEndPoint;
-    private CancellationTokenSource? _cts;
-    private UdpClient? _udpClient;
-
-    public event EventHandler<byte[]>? MessageReceived;
-
-    public UdpClientWrapper(int port)
+    public class UdpClientWrapper : IUdpClient
     {
-        _localEndPoint = new IPEndPoint(IPAddress.Any, port);
-    }
+        private readonly IPEndPoint _localEndPoint;
+        private CancellationTokenSource? _cts;
+        private UdpClient? _udpClient;
 
-    public async Task StartListeningAsync()
-    {
-        _cts = new CancellationTokenSource();
-        Console.WriteLine("Start listening for UDP messages...");
+        public event EventHandler<byte[]>? MessageReceived;
 
-        try
+        public UdpClientWrapper(int port)
         {
-            _udpClient = new UdpClient(_localEndPoint);
-            while (!_cts.Token.IsCancellationRequested)
+            _localEndPoint = new IPEndPoint(IPAddress.Any, port);
+        }
+
+        public async Task StartListeningAsync()
+        {
+            _cts = new CancellationTokenSource();
+            Console.WriteLine("Start listening for UDP messages...");
+
+            try
             {
-                UdpReceiveResult result = await _udpClient.ReceiveAsync(_cts.Token);
-                MessageReceived?.Invoke(this, result.Buffer);
+                _udpClient = new UdpClient(_localEndPoint);
+                while (!_cts.Token.IsCancellationRequested)
+                {
+                    UdpReceiveResult result = await _udpClient.ReceiveAsync(_cts.Token);
+                    MessageReceived?.Invoke(this, result.Buffer);
 
-                Console.WriteLine($"Received from {result.RemoteEndPoint}");
+                    Console.WriteLine($"Received from {result.RemoteEndPoint}");
+                }
+            }
+            catch (OperationCanceledException)
+            {
+                //empty
+            }
+            catch (Exception ex)
+            {
+                Console.WriteLine($"Error receiving message: {ex.Message}");
             }
         }
-        catch (OperationCanceledException ex)
-        {
-            //empty
-        }
-        catch (Exception ex)
-        {
-            Console.WriteLine($"Error receiving message: {ex.Message}");
-        }
-    }
 
-    public void StopListening()
-    {
-        try
-        {
-            _cts?.Cancel();
-            _udpClient?.Close();
-            Console.WriteLine("Stopped listening for UDP messages.");
-        }
-        catch (Exception ex)
+        public void StopListening()
         {
-            Console.WriteLine($"Error while stopping: {ex.Message}");
+            try
+            {
+                _cts?.Cancel();
+                _cts?.Dispose();
+                _udpClient?.Close();
+                Console.WriteLine("Stopped listening for UDP messages.");
+            }
+            catch (Exception ex)
+            {
+                Console.WriteLine($"Error while stopping: {ex.Message}");
+            }
         }
-    }
 
-    public void Exit()
-    {
-        try
-        {
-            _cts?.Cancel();
-            _udpClient?.Close();
-            Console.WriteLine("Stopped listening for UDP messages.");
-        }
-        catch (Exception ex)
-        {
-            Console.WriteLine($"Error while stopping: {ex.Message}");
-        }
-    }
+        public void Exit() => StopListening();
 
-    public override int GetHashCode()
-    {
-        var payload = $"{nameof(UdpClientWrapper)}|{_localEndPoint.Address}|{_localEndPoint.Port}";
+        public override int GetHashCode()
+        {
+            var payload = $"{nameof(UdpClientWrapper)}|{_localEndPoint.Address}|{_localEndPoint.Port}";
 
-        using var md5 = MD5.Create();
-        var hash = md5.ComputeHash(Encoding.UTF8.GetBytes(payload));
+            var hash = MD5.HashData(Encoding.UTF8.GetBytes(payload));
 
-        return BitConverter.ToInt32(hash, 0);
+            return BitConverter.ToInt32(hash, 0);
+        }
     }
-}
\ No newline at end of file
+}
diff --git a/NetSdrClientAppTests/NetSdrClientAppTests.csproj b/NetSdrClientAppTests/NetSdrClientAppTests.csproj
index 3cbc46a..eb99533 100644
--- a/NetSdrClientAppTests/NetSdrClientAppTests.csproj
+++ b/NetSdrClientAppTests/NetSdrClientAppTests.csproj
@@ -11,6 +11,10 @@
 
   <ItemGroup>
     <PackageReference Include="coverlet.collector" Version="6.0.0" />
+    <PackageReference Include="coverlet.msbuild" Version="10.0.1">
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
     <PackageReference Include="Moq" Version="4.20.72" />
     <PackageReference Include="NUnit" Version="3.14.0" />
diff --git a/NetSdrClientAppTests/NetSdrClientTests.cs b/NetSdrClientAppTests/NetSdrClientTests.cs
index ad00c4f..b52e77e 100644
--- a/NetSdrClientAppTests/NetSdrClientTests.cs
+++ b/NetSdrClientAppTests/NetSdrClientTests.cs
@@ -115,5 +115,29 @@ public async Task StopIQTest()
         Assert.That(_client.IQStarted, Is.False);
     }
 
+    [Test]
+    public async Task StopIQNoConnectionTest()
+    {
+        // act — no ConnectAsync, so Connected is false
+        await _client.StopIQAsync();
+
+        // assert
+        _tcpMock.Verify(tcp => tcp.SendMessageAsync(It.IsAny<byte[]>()), Times.Never);
+        _tcpMock.VerifyGet(tcp => tcp.Connected, Times.AtLeastOnce);
+    }
+
+    [Test]
+    public async Task ChangeFrequencyAsyncTest()
+    {
+        // arrange
+        await ConnectAsyncTest(); // 3 setup messages
+
+        // act
+        await _client.ChangeFrequencyAsync(20_000_000, 1);
+
+        // assert — 4th SendMessageAsync for frequency change
+        _tcpMock.Verify(tcp => tcp.SendMessageAsync(It.IsAny<byte[]>()), Times.Exactly(4));
+    }
+
     //TODO: cover the rest of the NetSdrClient code here
 }
diff --git a/NetSdrClientAppTests/NetSdrMessageHelperTests.cs b/NetSdrClientAppTests/NetSdrMessageHelperTests.cs
index b40fff7..285b694 100644
--- a/NetSdrClientAppTests/NetSdrMessageHelperTests.cs
+++ b/NetSdrClientAppTests/NetSdrMessageHelperTests.cs
@@ -64,6 +64,46 @@ public void GetDataItemMessageTest()
             Assert.That(parametersBytes.Count(), Is.EqualTo(parametersLength));
         }
 
+        [Test]
+        public void TranslateMessageRoundTripTest()
+        {
+            // arrange — build a SetControlItem message then parse it back
+            var parameters = new byte[] { 0x01, 0x02, 0x03, 0x04, 0x05 };
+            var msg = NetSdrMessageHelper.GetControlItemMessage(
+                NetSdrMessageHelper.MsgTypes.SetControlItem,
+                NetSdrMessageHelper.ControlItemCodes.ReceiverFrequency,
+                parameters);
+
+            // act
+            bool success = NetSdrMessageHelper.TranslateMessage(msg,
+                out var type, out var itemCode, out _, out var body);
+
+            // assert
+            Assert.That(success, Is.True);
+            Assert.That(type, Is.EqualTo(NetSdrMessageHelper.MsgTypes.SetControlItem));
+            Assert.That(itemCode, Is.EqualTo(NetSdrMessageHelper.ControlItemCodes.ReceiverFrequency));
+            Assert.That(body, Is.EqualTo(parameters));
+        }
+
+        [Test]
+        public void GetSamples16BitReturnsCorrectCountTest()
+        {
+            // 6 bytes → 3 samples of 16 bits
+            var body = new byte[] { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06 };
+
+            var samples = NetSdrMessageHelper.GetSamples(16, body).ToList();
+
+            Assert.That(samples.Count, Is.EqualTo(3));
+        }
+
+        [Test]
+        public void GetSamplesThrowsForOversizedBitsTest()
+        {
+            // 40 bits / 8 = 5 bytes > 4 → ArgumentOutOfRangeException
+            Assert.Throws<ArgumentOutOfRangeException>(() =>
+                NetSdrMessageHelper.GetSamples(40, new byte[8]).ToList());
+        }
+
         //TODO: add more NetSdrMessageHelper tests
     }
 }
\ No newline at end of file