Why am I getting an Exception with the message “Invalid setup on a non-virtual (overridable in VB) member…”?

Question

I have a unit test where I have to mock a non-virtual method that returns a bool type

public class XmlCupboardAccess
{
    public bool IsDataEntityInXmlCupbo         


        

Answer 1

Moq cannot mock non-virtual methods and sealed classes. While running a test using mock object, MOQ actually creates an in-memory proxy type which inherits from your "XmlCupboardAccess" and overrides the behaviors that you have set up in the "SetUp" method. And as you know in C#, you can override something only if it is marked as virtual which isn't the case with Java. Java assumes every non-static method to be virtual by default.

Another thing I believe you should consider is introducing an interface for your "CupboardAccess" and start mocking the interface instead. It would help you decouple your code and have benefits in the longer run.

Lastly, there are frameworks like : TypeMock and JustMock which work directly with the IL and hence can mock non-virtual methods. Both however, are commercial products.