Your real friends who are those that are there though thick and thin and can always make time to come and see you every once in a while. Fake friends likely wont do this. Though remember the saying "Ain't no enemy like an ex best friend".
If you want to find out who your tightest friends are, put out a 2-3 week notice that you are moving your house and you need volunteers to carry your furniture.
Those who bother to show up are definitely your true friends

Lol. It's the little things like this that you can do to gauge who your true friends are. True friends will go out if their way to help a friend in need and not expect anything in return. Another is who will come see you if you're in hospital....... though make sure they're not just doing it so they can post some selfies on Instagram or Facebook to show off and make out how much of a good friend they are lol.