Rasmus Hojlund struck early to give United the lead, before the Gunners hit back through Gabriel Jesus and Gabriel Martinelli.
Speaking after the 2-1 preseason win, Arteta said: "A really good test for us. Playing in a different stadium, different pitch conditions, four meters narrower, five metres shorter, against a top opponent. We were 1-0 down and to play in this context is really good for us because we have to see what it’s like and adapt. So really pleased.
"It’s a test. There’s not three points, but there’s a lot on the table. I think you could see that. I think Man Utd as well competed at the highest level. This is what you want as well. If you want to get prepared for the demands we have in the league and Champions League, you’d better have a good understanding of where your team is as quick as possible."
On Gabriel Jesus, the manager also said: "He looks really good. He looks really sharp. He has changed a lot of things over the summer. He has come in top condition again. And when you have that baseline, other things can be built but without that foundation you don’t have a player. He needs to be in that condition to get the best out of him. He has realised that. And I’m really happy with what he’s shown today again.
"That is a question for him (what's changed). But I know that. It is a fact and you can see. The way he looks, his rhythm, his sharpness, the way he is moving. And you can see in his eyes as well that there is again some spark there because he has got now a point to prove and that is good.
"I think that motivation has to come within himself, with his self demands and how much better he is able to make the team. He has shown it. He transformed the energy and the belief of that team and he has got it there. If he is waiting for something external to motivate him, I think it is going to be for a really short period. If it something internally that is happening, that is going to last long and it is going to be consistent. Hopefully that is the case."