measure of friendship

Just exactly how can you tell if a person's a friend or if it's just a one-way street?

I've been forced to evaluate my definition of friendship when a friend of mine and I had an argument over keeping promises. He's been promising a lot of things the past few months but has yet to keep one. I can understand if circumstances prevent people from keeping their word, but I find it difficult to accept that a person would keep none at all.

It would seem unfair that whenever he asks for a favor, he demands that it be done immediately. However, when I ask for a favor, he'd say "yes" but do it in his own time (for as long as its convenient) or, more often than not, back out at the last minute. Sometimes I'd wish he never said "yes" at all, that way I won't expect anything from him.

Am I (over)expecting from my friends? I truly feel that the only way you'd know if you can count on someone is that if you can expect them to keep their word. How then could you possibly trust someone if this is not the case?

Or am I just thinking that people owe it to me to keep their word because I've kept mine to them?