There's a saying in in the Mandarin Culture that goes "Only age and winter separates pine and cypress, only hardship reveals a true friend"

"岁寒知松柏，患难见真情"

It's easy to know a real friend from the fake over time. Good times? they're all around. Bad times? none to be found.

But even without the passage time you can kinda tell the character of a person based on their motive to be around you.

"friends" are hard to find. What I have in bulk are acquaintance, people that i interact with and get along but aren't the ones that i'll think of when in need of help. Sometimes it's very easy to sniff out person's intention when interacting with you. Just as you have ulterior motive to cosy up to someone.

One sure fire litmus test though is to go mountain hiking with them. Not the small hills too, it has to be trails that take at least a whole day to complete. You can tell alot by what a person (even yourself) do when mountain hiking.

Lots of unorthodox businessowners actually does this before settling on a business partnership or hiring a new crucial employee too! It works 100x better than any superficial interview.