inline Stream& operator<<(Stream& s,int v) {s.print(v);return s;}
inline Stream& operator<<(Stream& s,const char* v) {s.print(v);return s;}
//.. add some more members as needed

after this we can go in old stream lazy c++ stream style:

Serial<<"Counter: "<<cnt<<" units\n\r";

instead of the boring:

Serial.print("Counter: ");
Serial.print(cnt);
Serial.println(" units\n\r");

happy coding

We have published ongoing work at https://github.com/neu-rah/Arduino-VirtualPins

Its now possible to test virtual pins.