Each of us defines what it means to be "good friend".
Only the individual involved can surmise if the person they're associating with is a "true friend" in their book.
Generally speaking one expects their friend to take an interest in their life. Lend you their ears or shoulders to cry on when things aren't great, be the first to congratulate or offer ideas to celebrate your victories and vice versa. A true friend has your best interest at heart and wants only the best for you.
A false friend on the other hand may not ever call you unless (they) need or want something. If you don't initiate contact you often will not hear from them. Instead of dispelling rumors about you they will feed the rumors or look for ways to tear you down instead of building you up. A false friend may covet your spouse or your life in general.
They're with you for as long as you can benefit them. You're always the giver and they're always the taker. It's a one sided friendship.