No, this season is not "the test". He's an established world class player, and won't need to prove anything. Besides perhaps, providing in the Champions League.
But, I hope you are right actually, because without Zlatan on his best game, Inter will be back to their old mediocre ways. He means everything to their game. Ibrahimovic is a winner, if you could just put your bias against his personality aside for a second, you'd see that too.