#include <iostream>

class Parent
{
public:
    Parent() { ; }
    virtual void function() { std::cout << "Parent::function" << std::endl;; }
};

class Child : public Parent
{
public:
    Child() { ; }
    void function() { std::cout << "Child::function" << std::endl; }
};

class Test
{
public:
     Test(Parent& c) { c.function(); }
};

int main()
{
    Child c;
    Parent& p = c;
    Test t(p);
}