The above posts give good explanations already, I just like to add the following:
For the above given hash I get the following constant order of keys:

Zero
Two
One
[download]

I think the reason for your "constant"/"deterministic" behavior is that your test hash is very very small so that there aren't much different ways to order the keys. It's just by chance that the first given key is the first returned. As soon you have more keys a different key is the first returned.