Friendships will be lost and forged through life. Its the circule of life. The good friends will stick by you no matter the situation especially if they realise you need a good friend to listen to you.
I've noticed that you can usually tell who is more of a friend by how much time you can spend around them when you're both bored as hell (not at school or a job, but in your own time). When there's no need to plan some huge event because you enjoy each other's company enough to do nothing.
There is an even easier way. If your friend calls you bud, man, buddy, or dud. They aren't your friends either. Many people think it is, but they aren't. Friends you make some. You keep them. You lose them. Its as simple as that. Friends don't stay friends forever.