TDD and Mocking out TcpClient

Question

How do people approach mocking out TcpClient (or things like TcpClient)?

I have a service that takes in a TcpClient. Should I wrap that in something else more mocka

Answer 1

I think @Hitchhiker is on the right track, but I also like to think about abstracting out things like that just a step further.

I wouldn't mock out the TcpClient directly, because that would still tie you too closely to the underlying implementation even though you've written tests. That is, your implementation is tied to a TcpClient method specifically. Personally, I would try something like this:

   [Test]
    public void TestInput(){

       NetworkInputSource mockInput = mocks.CreateMock();
       Consumer c = new Consumer(mockInput);

       c.ReadAll();
    //   c.Read();
    //   c.ReadLine();

    }

    public class TcpClientAdapter : NetworkInputSource
    {
       private TcpClient _client;
       public string ReadAll()
       { 
           return new StreamReader(_tcpClient.GetStream()).ReadToEnd();
       }

       public string Read() { ... }
       public string ReadLine() { ... }
    }

    public interface NetworkInputSource
    {
       public string ReadAll(); 
       public string Read();
       public string ReadLine();
    }

This implementation will decouple you from Tcp related details altogether (if that is a design goal), and you can even pipe in test input from a hard coded set of values, or a test input file. Very hand if you are on the road to testing your code for the long haul.