Question

I have this property:

    public SubjectStatus Status
    {
        get { return status; }
        set
        {
            if (Enum.IsDefined(typeof(SubjectStatus), value))
            {
                status = value;
            }
            else
            {
                Debug.Fail("Error setting Subject.Status", "There is no SubjectStatus enum constant defined for that value.");
                return;
            }
        }
    }

and this unit test

    [Test]
    public void StatusProperty_StatusAssignedValueWithoutEnumDefinition_StatusUnchanged()
    {
        Subject subject = new TestSubjectImp("1");

        //  assigned by casting from an int to a defined value
        subject.Status = (SubjectStatus)2;
        Assert.AreEqual(SubjectStatus.Completed, subject.Status);            

        //  assigned by casting from an int to an undefined value
        subject.Status = (SubjectStatus)100;
        //  no change to previous value
        Assert.AreEqual(SubjectStatus.Completed, subject.Status);            
    }

Is there a way I can prevent Debug.Fail displaying a message box when I run my tests, but allow it to show me one when I debug my application?

Answer 1

The standard way I’ve always done this is to create a plugin for NUnit. The plugin simply unregisters the default trace listener and registers a replacement that throws an exception when Assert/Trace.Fail is triggered. I like this approach because tests will still fail if a assert trips, you don’t get any message boxes popping up and you don’t have to modify your production code.

Edit — here’s the plugin code in its entirety. You’re on your own for building the actual plugin though — check the NUnit site 🙂

[NUnitAddin]
public class NUnitAssertionHandler : IAddin
{
    public bool Install(IExtensionHost host)
    {
        Debug.Listeners.Clear();
        Debug.Listeners.Add(new AssertFailTraceListener());
        return true;
    }

    private class AssertFailTraceListener : DefaultTraceListener
    {
        public override void Fail(string message, string detailMessage)
        {
            Assert.Fail("Assertion failure: " + message);
        }

        public override void Fail(string message)
        {
            Assert.Fail("Assertion failure: " + message);
        }
    }
}