如何模拟扩展类并实现接口的对象？

Question

I have this class:

public class BaseFoo
{
    public bool BoolProp { get; set; }
}

public interface IFoo {
    void Method();
}

public class FooClass : BaseFoo, IFoo
{
    public void Method()
    {
        // DoSomething
    }
}

public class MyClass
{
    IFoo foo; // 
    public MyClass(IFoo foo)
    {
        this.foo = foo;
    }

    public void DoSomething()
    {
        if (((FooClass)foo).BoolProp)
        {
            // yeah
        }
        else
        {
            //bad
        }
    }
}

My scenario is:

    void main()
    {
        MyClass obj = new MyClass(new FooClass());
        obj.DoSomething();
    } 

I'd like to create a mock object for the IFoo interface that allows me to mock the BaseFoo class too because I need to always avoid running the "else" branch of the "if (((FooClass)foo).BoolProp)" in the MyClass.DoSomething() method.
So, how can I create a mock object that allows me to mock the behaviour of BaseFoo.BoolProp used in MyClass (that will take a mock object of IFoo)?
I did that without any result because the "BoolProp" is not virtual and I can't change it as it is part of a .NET Framework class:

  var cMock = new Mock<BaseFoo>();
  var iMock = cMock.As<IFoo>();

  cMock.Setup(c => c.BaseProp).Returns(true);
  MyClass myClass = new MyClass(iMock.Object);

Answer 1

What your design is really saying is that your class MyClass does not have a dependency on IFoo , it has a dependency on a class instance derived from BaseFoo and implementing IFoo . In this case it is probably best that you introduce a unifying interface which you can then use as a dependency and mock:

interface IFooBar
{
  bool BoolProp { get; set; }
  void Method();
}  

Answer 2

How about declaring an abstract class (BaseFooFoo?) that derives from BaseFoo and implements IFoo. Then you could show BaseFooFoo to moq.