What character do you use to test new characters?

Jaune Arc JUS. His AI is abysmal, and if any character can get over his shield bash spam, then I know they're a keeper.

I have seen before some characters with adjustable difficult in their files, and some of them have 8 difficult with 4 being pre set for vs player and 4 vs AI, you maybe loosing some characters that could be good opponents

This is probably a basic answer but I usually use kung fu man idk he's just such a classic.