Question

I am new to moq and I was trying to test a controller (MVC) behaviour that when the view raises a certain event, controller calls a certain function on model, here are the classes –

public class Model
{
    public void CalculateAverage()
    {
        ...
    }

    ...
}

public class View
{
    public event EventHandler CalculateAverage;

    private void RaiseCalculateAverage()
    {
        if (CalculateAverage != null)
        {
            CalculateAverage(this, EventArgs.Empty);
        }
    }

    ...
}

public class Controller
{
    private Model model;
    private View view;

    public Controller(Model model, View view)
    {
        this.model = model
        this.view = view;
        view.CalculaeAverage += view_CalculateAverage;
    }

    priavate void view_CalculateAverage(object sender, EventArgs args)
    {
        model.CalculateAverage();
    }
}

and the test –

[Test]
public void ModelCalculateAverageCalled()
{
    Mock<Model> modelMock = new Mock<Model>();
    Mock<View> viewMock = new Mock<View>();
    Controller controller = new Controller(modelMock.Object, viewMock.Object);
    viewMock.Raise(x => x.CalculateAverage += null, new EventArgs.Empty);
    modelMock.Verify(x => x.CalculateAverage());
    //never comes here, test fails in above line and exits
    Assert.True(true);
}

The issue is that the test is failing in the second last line with “Invocation was not performed on the mock: x => x.CalculateAverage()”. Another thing I noticed is that the test terminates on this second last line and the last line is never executed. Am I doing everything correct?

Answer 1

Please find below working snippet. The difference is that “CalculateAverage” is declared as virtual. The reason is that Moq creates runtime wrapper over “Mock” classes and overrides its beheviour. But if method is not virtual, then it is just impossible.

    public class Model
    {
        public virtual void CalculateAverage()
        {
        }
    }

    public class View
    {
        public virtual event EventHandler CalculateAverage;
    }

    public class Controller
    {
        private Model model;
        private View view;

        public Controller(Model model, View view)
        {
            this.model = model;
            this.view = view;
            view.CalculateAverage += view_CalculateAverage;
        }

        private void view_CalculateAverage(object sender, EventArgs args)
        {
            model.CalculateAverage();
        }
    }

    [TestFixture]
    public class MvcTest
    {
        [Test]
        public void ModelCalculateAverageCalled()
        {
            var modelMock = new Mock<Model>();
            var viewMock = new Mock<View>();

            var controller = new Controller(modelMock.Object, viewMock.Object);

            viewMock.Raise(x => x.CalculateAverage += null, EventArgs.Empty);
            modelMock.Verify(x => x.CalculateAverage());
        }
    }