Question

Is it possible to use Moq to mock an object that implements an interface and abstract class?

I.e.:

public class MyClass: SomeAbstractClass, IMyClass

Can you mock this?

Answer 1

You can mock any interface, and any abstract or virtual members. That’s basically it.

This means that the following are absolutely possible:

var imock = new Mock<IMyClass>();
var aMock = new Mock<SomeAbstractClass>();

If the members inherited from SomeAbstractClass aren’t sealed, you can also mock MyClass:

var mcMock = new Mock<MyClass>();

Whether this makes sense or not depends on the implementation of MyClass. Let’s say that SomeAbstractClass is defined like this:

public abstract class SomeAbstractClass
{
    public abstract string GetStuff();
}

If the GetStuff method in MyClass is implemented like this, you can still override it:

public override string GetStuff()
{
    return "Foo";
}

This would allow you to write:

mcMock.Setup(x => x.GetStuff()).Returns("Bar");

since unless explicitly sealed, GetStuff is still virtual. However, had you written GetStuff like this:

public override sealed string GetStuff()
{
    return "Baz";
}

You wouldn’t be able to mock it. In that case, you would get an exception from Moq stating that it’s an invalid override of a non-virtual member (since it’s now sealed).