The apartment is exactly as shown on the pictures, very clean and freshly renovated. It is perfect for two couples : each room has its own bathroom, the beds are good quality and the triple-glazed windows stop the noises from the street.
Testaccio is a central lively neighborhood and the flat is 3-minute walk from the local market, 1 minute from a tram and bus stop.
Sergio is very nice and helpful and makes himself available when needed.
I would really recommend his flat and I would definitely come back if I have a chance.