How big is his pasture he's in? And what are you feeding him, and how much? Too much feed, with not enough exercise can make a horse hard to handle.

Yes, he's going to test you. It's a given with any horse. You need to show him you are the leader of your little herd of two. And that means making him listen and do what you tell him to. Don't be afraid to bop him a good one with the end of your lead rope if necessary. Sometimes it's a good wake up call to get their attention.