[Matthias247]

From my point of view a benefit for virtual calls is toolability. If you have an abstract interface, it’s pretty easy to either directly create mocks for it in the test file, or use sth like gmock. If you go through the link completely different implementation route, you might need to create and link a different library which contains the faked implementation for several test cases. It also works well with pure header code.

[mehrdadn]

If I understand you correctly aren't you violating the initial assumption that there are only 2 implementations, one for production and one for testing? At which point, you're answering a different question...