Stub one method of class and let other real methods use this stubbed one

Question

I have a TimeMachine class which provides me current date/time values. The class looks like this:

public class TimeMachine
{
    public virtual DateTime GetCurrentDateTime(){ return DateTime.Now; };
    public virtual DateTime GetCurrentDate(){ return GetCurrentDateTime().Date; };
    public virtual TimeSpan GetCurrentTime(){ return GetCurrentDateTime().TimeOfDay; };
}

I'd like to use TimeMachine stub in my tests in such way that I'd just stub the GetCurrentDateTime method and let the other 2 methods use the stubbed GetCurrentDateTime method so as I don't have to stub all the three methods. I tried to do write the test like this:

var time = MockRepository.GenerateStub<TimeMachine>();
time.Stub(x => x.GetCurrentDateTime())
    .Return(new DateTime(2009, 11, 25, 12, 0, 0));
Assert.AreEqual(new DateTime(2009, 11, 25), time.GetCurrentDate());

But the test fails. GetCurrentDate returns default(DateTime) instead of using GetCurrentDateTime stub internally.

Is there any approach I could use to achieve such behavior or is it just some basic conceptual feature of RhinoMocks I don't catch at the moment? I know I could just get a rid of those two GetDate/Time methods and inline the .Date/.TimeOfDay usage, but I'd like to understand whether this is possible at all.

Answer 1

If the method is marked as virtual, a Stub will not call the original method, even if you didn't Stub the method. You can force RhinoMocks to call the original method by doing:

var time = MockRepository.GenerateStub<TimeMachine>();
time.Stub(x => x.GetCurrentDateTime()).Return(new DateTime(2009, 11, 25, 12, 0, 0));

time.Stub(x => x.GetCurrentDate()).CallOriginalMethod(OriginalCallOptions.NoExpectation);

Assert.AreEqual(new DateTime(2009, 11, 25), time.GetCurrentDate());

It's the third (seperated) line that makes RhinoMocks call the underlying, original method.

Answer 2

Change your TimeMachine to an abstract class:

public abstract class TimeMachine
{
    public abstract DateTime GetCurrentDateTime();
    public DateTime GetCurrentDate(){ return GetCurrentDateTime().Date; };
    public TimeSpan GetCurrentTime(){ return GetCurrentDateTime().TimeOfDay; };
}

For production purposes, you can create a concrete implementation of TimeMachine like this:

public class SystemTimeMachine : TimeMachine
{
    public override DateTime GetCurrentDateTime()
    {
        return DateTime.Now;
    }
}

All classes consuming TimeMachine can now be injected with the abstraction, but in production you can wire up your object graph with SystemTimeMachine.