Thats a magneto, no points or electronics.

I'm no expert at them, but I can work it.
As the magnet passes the coil a spark is generated.

There is probably a wire attached to the coil, if grounded (maybe NOT grounded) it will not fire, this is the key shut off.

Beyond that I don't think there is any way to test except to replace and if it works now.

__________________
KLK, MCSE

1990 500SL

I was always taught to respect my elders.
I don't have to respect too many people anymore.