There are only 2 grounding points on the bike.
1- Under the voltage reg to the frame, and
2- Under the coils up front.
There is no way to test a CDI other then swap in one that you know is good.
When I was running into electrical problems with my bike, I pulled the entire harness, unwrapped it, made sure everything matched up, did away with all the TORS shit, and wrapped it back up. I havent had an electrical problem since. The electrical fAq is awesome, and this: http://www.dfn.com/benkaren/banshwdc2.jpg picture is especially helpful. It gives you the bare bones of what you would need to do to make the bike run.