It means you will have to templatize your production code. Using your example:
CSumWind class definition:
class CSumWnd : public CBaseWnd
{
private:
bool MethodA()
};
Mocked CSumWnd class definition:
class MockCSumWnd : public CBaseWnd
{
private:
MOCK_METHOD(MethodA, bool());
};
Production class which have to be tested with mocked class CSumWind. Now it becomes templated to provide using CSumWind class in production code and MockCSumWnd class in tests.
template <class CSumWndClass>
class TestedClass {
//...
void useSumWnd(const CSumWndClass &a);
private:
CSumWndClass sumWnd;
};
Instantiation of TestedClass in production:
TestedClass <CSumWnd> obj;
Instantiation of TestedClass object in test executable:
TestedClass <MockCSumWnd> testObj;