1 of the ways to know if that person is your true friend is 'help'. If you are in trouble and a friend willing to help you then that person is trustworthy and a true friend. If you're financially troubled and your friend still helps you, he/she qualified to be your BFF.
Why asking a friend to help you when you can ask money from your family? Family will help you if you're ever in any trouble because of special bond. Your ties between family won't be easy to cut off like how easy a friend is.
You can see how your friends giving excuses for unable to help you and their attitude/personality turn 180° when you in money pinch. Even family sometimes like that but they will not ignore us because we are family. Blood is thicker than water.
People always say 'my BFF is my sis/bro' and that's right. A friend helps you is your true friend and upgrade your friendship level to BFF which is equal to family.
Value your friendship!