Question

I’m trying to practice unit testing in the TDD way so I created a set of interfaces that I thought could be tested somewhat independently. I’m not sure I succeeded but I’m now at the point where I’m pretty sure it’s time for a mocking framework. I learn best from example and I figure someone who’s very proficient will probably be able to translate this into one of them quickly (Moq or Rhino Mocks maybe? those are the ones I’ve found).

Unit Test:

    [TestMethod]
    public void RendererRendersEachWidgetByCallingBeginRenderThenEndRender()
    {
        // Mocks/Stubs
        ISpace space = new MockSpace();
        IWorld world = new MockWorld();
        IWidget widget1 = new MockWidget("widget1");
        IWidget widget2 = new MockWidget("widget2");
        world.Add(widget1);
        world.Add(widget2);

        // Object under test
        IRenderer target = new Renderer(world, space);
        target.Render();

        // verify BeginRender is called
        Assert.IsTrue((space as MockSpace).results.Contains("Begin Render " + widget1.Id));
        Assert.IsTrue((space as MockSpace).results.Contains("Begin Render " + widget2.Id));

        // verify EndRender is called
        Assert.IsTrue((space as MockSpace).results.Contains("End Render " + widget1.Id));
        Assert.IsTrue((space as MockSpace).results.Contains("End Render " + widget2.Id));

        // verify BeginRender is called before EndRender
        var orderedResults = (space as MockSpace).results.Select((s, i) => Tuple.Create(i, s));
        Assert.IsTrue(
            (orderedResults.Single(x => x.Item2 == "Begin Render " + widget1.Id).Item1) <
            (orderedResults.Single(x => x.Item2 == "End Render " + widget1.Id).Item1));
        Assert.IsTrue(
            (orderedResults.Single(x => x.Item2 == "Begin Render " + widget2.Id).Item1) <
            (orderedResults.Single(x => x.Item2 == "End Render " + widget2.Id).Item1));
    }

Answer 1

Here is a Rhino.Mocks version. I’ve taken liberties where the internals of the Renderer were unknown.

As you can see, there is a fair amount of setup involved, but in this case you won’t have had to create all those
mock object types manually.

[TestMethod]
public void RendererRendersEachWidgetByCallingBeginRenderThenEndRender()
{
    // Mocks/Stubs
      var orderedResultList = new List<string>();

    var space = MockRepository.GenerateStub<ISpace>();
      space.Stub(s => s.BeginRender(Arg<IWidget>.Is.Anything))
            .WhenCalled(x => orderedResultList.Add("Begin Render " + ((IWidget)x.Arguments[0]).Id));
      space.Stub(s => s.EndRender(Arg<IWidget>.Is.Anything))
            .WhenCalled(x => orderedResultList.Add("End Render " + ((IWidget)x.Arguments[0]).Id));

    var world = MockRepository.GenerateStub<IWorld>();

    var widget1 = MockRepository.GenerateStub<IWidget>();
      widget1.Stub(w => w.Id).Return("widget1"); // assuming no public setter for this property

    var widget2 = MockRepository.GenerateStub<IWidget>();
      widget2.Stub(w => w.Id).Return("widget2"); // assuming no public setter for this property

    var widgetList = new List<IWidget>{ widget1, widget2 };
      world.Stub(w => w.Widgets).Return(widgetList);

    // Object under test
    IRenderer target = new Renderer(world, space);
    target.Render();

    // verify BeginRender is called
      space.AssertWasCalled(s => s.BeginRender(Arg<IWidget>.Is.Same(widget1)));
      space.AssertWasCalled(s => s.BeginRender(Arg<IWidget>.Is.Same(widget2)));

    // verify EndRender is called
      space.AssertWasCalled(s => s.EndRender(Arg<IWidget>.Is.Same(widget1)));
      space.AssertWasCalled(s => s.EndRender(Arg<IWidget>.Is.Same(widget2)));

    // verify BeginRender is called before EndRender
    var orderedResults = orderedResultList.Select((s, i) => Tuple.Create(i, s));
    Assert.IsTrue(
        (orderedResults.Single(x => x.Item2 == "Begin Render " + widget1.Id).Item1) <
        (orderedResults.Single(x => x.Item2 == "End Render " + widget1.Id).Item1));
    Assert.IsTrue(
        (orderedResults.Single(x => x.Item2 == "Begin Render " + widget2.Id).Item1) <
        (orderedResults.Single(x => x.Item2 == "End Render " + widget2.Id).Item1));
}