I hate writing about 5-star places because then everyone else wants to stay there and I can't go back, and this is the situation with Stefania's place. This really is an outstanding apartment. It is beautifully and very recently renovated and every system in the apartment works perfectly.
The apartment has a long hallway/entrance; on one side are two rooms, one a bedroom and the other a living room (that has a sleeper sofa and wardrobe, so it can also be a bedroom). On the other side of the hall is a beautiful bathroom: nice sized, sink, shower, toilet, bidet. And at the end, the hallway opens up into a well-equipped kitchen with a small dining table. The kitchen also has the dishwasher and, unusual for Italy, a washer/dryer combination that works well (if slowly).
Every room, including the kitchen has climate control, individually controlled locally. Two big TVs (which I didn't use), comfortable and new bed.
Everything was immaculate. Stefania was very gracious and super helpful as well.
The apartment would be absolutely ideal for 2 people. For 3 or 4, it could be OK for a limited period of time, but it depends on whether you want to use the kitchen, because the dining table is really only big enough for 3, maybe 4 if you are squeezing.
What can I say negative about this apartment? Almost nothing. The building itself is not the most beautiful in Testaccio, but the apartment on the inside is much prettier than the building on the outside. There are windows that open, but no balcony (not uncommon in Teestaccio). But really, it's a very nice apartment and I highly recommend it.