Re: Modify pointed object method behaviour

I think this is mostly impossible, but just want to be sure.
Say that I have this 2 untouchable things:
void my_func(MyBase *baseptr){
      base_ptr->one();
      base_ptr->two();}

class MyBase{
      void one(){implemented}
      void two(){implemented}
};

And now I want to test if my_func works ok but I can't use a
MyBase object, one and two implementations are too heavy, I
could use anything that my_func accepts, it'd accept pointers
to derived.

So, as far as I know any implementation would hardcode
base_ptr->one to the MyBase::one and base_ptr->two MyBase::two
because they're not even virtual and that doesn't let me any
room to play, inheritance, etc....
There's nothing I could do with RTTI that would do the trick without
modifying MyBase or my_func.
Am I correct?