I do not know about the catnip magneto and CDI but on my stock china girl you can use a ohm meter to check both.
The above is copy pasted from
Just read this. http://kcsbikes.com/topic.asp?TOPIC_ID=623
motoredbikes.com
There are several posts on this forum regarding checking both with an ohm meter.
I also check mine with all the wires disconnected from each other when I check the CDI I disconnect the spark plug wire and test it from the screw that holds the wire on (black negative on the OHM meter and the red positive to the black input wire)