Trying to use a mock NetworkStream to fake out some data that would normally come over a network device. I want to make sure my test works without being dependent on outside piece of hardware.

ABDriver.cs

public class ABEthernetDriver
{
  /* Some other methods and properties, constructor */
  private ITcpClient _client;
  private INetworkStream _nstream;
  
  public void Connect()
  {
      _nstream = _client.GetStream();
      byte[] numArray = new byte[] {1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
      _responded[0] = false;
      try
      {
          //Signature: IAsyncResult BeginRead(byte[] buffer, int offset, int size, AsyncCallback callback, object state)
          _nstream.BeginRead(_readBuffer, 0, checked(_readBuffer.Length), DataReceived, _nstream);
          _nstream.Write(numArray, 0, checked(numArray.Length));
      }
      catch (Exception ex)
      {
          _log.ErrorFormat("Unable to connect to device at: {0}", ex.Message);
          throw;
      }
  }
  
  private void DataReceived(IAsyncResult ar)
  {
      try
      {
          _bytecount = _nstream.EndRead(ar);
          if (_bytecount == 0)
          {
              bool dataAvailable = _nstream.DataAvailable;
          }

          _receivedDataPacket.Clear();
          int num = checked(_bytecount - 1);
          for (int i = 0; i <= num; i++)
          {
              _receivedDataPacket.Add(_readBuffer[i]);
          }
          ProcessReceivedData();
      }
      catch (Exception ex)
      {
          _log.ErrorFormat("DataReceived failed to parse data: {0}", ex.Message);
      }
  }
}