My first personal insight on a true friendship was that the friend is not the person who helps you out in a difficult situation but the one who can enjoy your joys. Indeed I have noticed that many people are happy to help out, in some or other way if anything bad happens. However not many are able to enjoy what you enjoy.
Recently I thought of another important friendship distinction:
A true friendship passes through the “money test”, and the false one not. How many stories we all have heard/experienced when so-called best friends, being in a business situation of making and sharing money, suddenly part and fight? How many seemingly stable and good relationships have been brocken when money came into the play?
Luckily I never experienced that, in fact just the opposite: one of my best, long-term friends is at the same time my employer and the money issue makes no impact on our wonderful relationship. But I know of many opposite cases.
Somehow or rather, money has its power spell over relatioshiops. Therefore it is the best friendship test.