He doesn't really have any terrible bad matchups. He has some odd off the wall matches with people like ky because of the spam he can do, but mostly all is well. S-tier characters ( Slayer, Eddie, Baiken ) can give you some trouble sometimes. All you have to do is practice the matchup and you will start to see things that just flat out beat most of the things they try. Eddie and Slayer are my most played matchups and i must say i have improved tenfold from when i picked up Test a few months ago.
Learning to pull off the tk.BL loops, and the EXE FRC are especially important to his game. I have the tk down but the HS EXE FRCs are still uncertain for me. Good thing the move is soo good without the FRC too, or i would be getting annihilated nightly. Hope i helped you out, keep on practicing!!