Mocking a TwinCAT Ads Server, for unit testing code with ADS read/write requests.
With this Nuget package it is possible to test your code even if it is relying on TwinCAT.Ads.dll calls and dependencies on that library (e.g. TwinCAT.Ads.TypeSystem.SymbolFactory).
You don't need to setup a PLC or TwinCAT runtime to test your code, hence no special requirements on a build server.

• How-to
• Example
• Extensions

1. Setup mocking server

   ushort port = 12345;
   string portName = "MyTestAdsServer";
   using (var mockServer = new Mock(port, portName))   // ILogger optional
   {
       // ...
   }

2. Register Behaviors

    mockServer.RegisterBehavior(new ReadIndicationBehavior(1, 123,  Enumerable.Range(1,32).Select(i => (byte)i).ToArray()))
            .RegisterBehavior(new ReadIndicationBehavior(1, 1, Encoding.UTF8.GetBytes("acting as a ADS server")))
            .RegisterBehavior(new ReadIndicationBehavior(0, 0, null, AdsErrorCode.DeviceAccessDenied))
            .RegisterBehavior(new WriteIndicationBehavior(0, 0, 22));

   • Behaviors
     Behaviros like ReadIndicationBehavior are used as enpdpoint for a specific ADS call, e.g.

     new ReadIndicationBehavior(1, 123,  Enumerable.Range(1,32).Select(i => (byte)i).ToArray())

     A ReadAsync ADS call is made to IndexGroup=1, IndexOffset=123 with Length=32, in this case the server will return 32 bytes (0x01..0x20) to the client.

3. Test
   For example, the class we want to test:

   using System;
   using System.Linq;
   using System.Threading;
   using System.Threading.Tasks;
   
   namespace Sample
   {
       public class MyAdsClass
       {
           public MyAdsClass(int port)
           {
               Port = port;
           }
           public int Port { get; }
   
           private byte[] _buffer = new byte[32];
   
           public async Task<byte[]> GetValuesFilteredAsync(uint ig, uint io, Func<byte, bool> filterFunc)
           {
               using (var client = new TwinCAT.Ads.AdsClient())
               {
                   client.Connect(Port);
                   var result = await client.ReadAsync(ig, io, _buffer, CancellationToken.None);
                   if (result.Succeeded)
                       return _buffer.Where(x => filterFunc(x)).Select(x => x).ToArray();
               }
               return new byte[0];
           }
       }
   }

   Unit test:

   [TestMethod]
   public async Task Should_filter_even_and_odd_values()
   {
       // arrange
       ushort port = 12345;
       string portName = "MyTestAdsServer";
       using (var mockServer = new Mock(port, portName))   // ILogger optional
       {
           mockServer.RegisterBehavior(new ReadIndicationBehavior(1, 123, Enumerable.Range(1, 32).Select(i => (byte)i).ToArray()));
           var myAdsCls = new MyAdsClass(mockServer.ServerAddress.Port);
   
           // act
           var even = await myAdsCls.GetValuesFilteredAsync(1, 123, (x) => x % 2 == 0);
           var odd = await myAdsCls.GetValuesFilteredAsync(1, 123, (x) => x % 2 != 0);
   
           // assert
           Assert.IsTrue(even.SequenceEqual(new byte[] { 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32 }));
           Assert.IsTrue(odd.SequenceEqual(new byte[] { 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31 }));
       }
   }

// setup mocking server
ushort port = 12345;
string portName = "MyTestAdsServer";
using (var mockServer = new Mock(port, portName))
{
    var serverBuffer = new byte[65535];
    mockServer.RegisterBehavior(new ReadIndicationBehavior(1, 123,  Enumerable.Range(1,32).Select(i => (byte)i).ToArray()))
                .RegisterBehavior(new ReadIndicationBehavior(1, 1, Encoding.UTF8.GetBytes("acting as a ADS server")))
                .RegisterBehavior(new ReadIndicationBehavior(0, 0, null, AdsErrorCode.DeviceAccessDenied))
                .RegisterBehavior(new WriteIndicationBehavior(0, 0, 22));

    Console.WriteLine("Server up and running");

    // now the actual Ads Read/WriteRequests...

    // create TwinCAT Ads client
    using (var client = new AdsClient(logger))
    {
        // connect to our mocking server
        client.Connect(port);
        if (client.IsConnected)
        {
            var readBuffer = new byte[65535];
            var readMemory = new Memory<byte>(readBuffer);
            var writeBuffer = new byte[65535];
            var writeMemory = new Memory<byte>(writeBuffer);

            // 1st behavior
            var resRd = await client.ReadAsync(1, 123, readMemory[..32], CancellationToken.None);
            // 2nd behavior
            resRd = await client.ReadAsync(1, 1, readMemory, CancellationToken.None);
            Console.WriteLine(Encoding.UTF8.GetString(readMemory.Slice(0,resRd.ReadBytes).Span));
            // 3rd behavior
            resRd = await client.ReadAsync(0, 0, readMemory, CancellationToken.None);
            // 4th behavior
            var resWr = await client.WriteAsync(0, 0, writeMemory[..22], CancellationToken.None);
        }
    }
}

See SampleConsole and UnitTestSample for functional examples.

These extension methods are defined in project dsian.TwinCAT.Ads.Server.Mock.Extensions:

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