Unit Testing The Presenter (in an MVP Context) Using Mock Objects?

Question

Below is some code which is just the simplest MVP project I could make. How can I unit test the presenter using mock objects? Does a mock object mean a completely made up object? In this case, the presenter needs an instance of Form1, and Form1 inherits from the interface IForm1. Does that mean I need to create fake duplicates of Form1 and IForm1 that are used to unit test my presenter?

I feel like I'm really close to understanding what's going on here, I really want to get my head around unit testing an MVP model, I think it will be greatly beneficial for the system I'm working on.

Thanks!

using System;
using System.Windows.Forms;

namespace MVP_Testing {
    public partial class Form1 : Form, IForm1 {
        private Presenter p;
        public Form1() {
            InitializeComponent();
            p = new Presenter(this);
        }

        #region Interface
        public string Value1 {
            get { return inputValue1.Text; }
        }
        public string Value2 {
            get { return inputValue2.Text; }
        }
        public string Result {
            set { textBoxResult.Text = value; }
        }
        #endregion

        private void buttonCalculate_Click(object sender, EventArgs e) {
            p.DoCalculation();
        }
    }

    public interface IForm1 {
        string Value1 { get; }
        string Value2 { get; }
        string Result { set; }
    }

    public class Presenter {
        private readonly IForm1 _iform1;
        public Presenter(IForm1 iform1) {
            _iform1 = iform1;
        }

        public void DoCalculation() {
            int value1 = Convert.ToInt16(_iform1.Value1);
            int value2 = Convert.ToInt16(_iform1.Value2);
            _iform1.Result = (value1 * value2).ToString();
        }
    }
}

Answer 1

To do the mocking you should use a mocking framework, there are plenty of good ones to choose from such as RhinoMock, Moq, this post on stack-overflow mentions all the good mocking frameworks. Choose one that best fits your needs.

The following example is how I would do this using RhinoMocks:

public void CorrectResult()
{
    //setup the mock object
    var mockedView = MockRepository.GenerateMock<IForm1>();
    mockedView.Expect(view => view.Value1).Return("2");
    mockedView.Expect(view => view.Value2).Return("3");

    //make the call to do the calculation
    var p = new Presenter(mockedView);
    p.DoCalculation();

    //check that the Result property was set to 6
    mockedView.AssertWasCalled(view => view.Result = "6");
}