Why does the following test fail using Mbunit and Rhino mocks?

Question

I am playing around with MbUnit and Rhino Mocks and made a simple test. It may be poorly designed code, but I am more focused on just seeing if I can get the test to pass. Basically, When the engine light of a car is on, the car should an oil change. Here is code:

public interface ICar
{
    bool EngineLight { get; set; }
    void GetOilChange();
    bool CheckEngineLight(ICar car);
}

public class Car : ICar
{
    public bool EngineLight { get; set; }

    public void GetOilChange()
    {
    }

    public bool CheckEngineLight(ICar car)
    {
        if (car.EngineLight)
            GetOilChange();
            return true;

        return false;
    } 
}

[TestFixture]
public class CarTests
{
[Test]
    public void WhenEngineLightIsOnGetOilChange()
    {
        var carMock = MockRepository.GenerateMock<ICar>();
        carMock.Stub(x => x.EngineLight).Return(true);

        Assert.AreEqual(true, new Car().CheckEngineLight(carMock)); //This passes

        carMock.AssertWasCalled(x => x.GetOilChange()); //This fails
    }
 }

Answer 1

First off, this code has a bug. Add in the {} around the IF:

public bool CheckEngineLight(ICar car)
    {
        if (car.EngineLight)
        {
            car.GetOilChange();
            return true;
        }

        return false;
    } 

The reason it fails is because you are calling new Car().CheckEngineLight ... and the new Car() is calling GetOilChange ... the carMock is not calling GetOilChange. Change the code to car.GetOilChange() (see it in the code above).

The fact that you are passing a Car object into a method on the Car Object is very confusing. Why not change the code to this:

public class Car : ICar
{
    public bool EngineLight { get; set; }

    public void GetOilChange()
    {
    }

    public bool CheckEngineLight()
    {
        if (EngineLight)
        {
            GetOilChange();
            return true;
        }

        return false;
    } 
}

Change your test to:

[Test]
    public void WhenEngineLightIsOnGetOilChange()
    {
        var carMock = MockRepository.GenerateMock<ICar>();
        carMock.Stub(x => x.EngineLight).Return(true);

        Assert.AreEqual(true, carMock.CheckEngineLight()); 

        carMock.AssertWasCalled(x => x.GetOilChange()); 
    }
 }