Couple months ago got a home made coil tester
0 to 3 amp guage got it out tested all my coils all where 1.2 to 2 amps using 12volt battery.
Like know little more about testing/adjusting them.
This doesnt mean i stop sending my coils to a pro
Just means i can check what comes in
MTFCA book: The Electrical System.
That tester will tell you if your coils are bad, as no sparks will show.
It cannot tell you how good the coils are, as a good Mag can put out 24 to 36 volts for a much hotter spark, you cannot tell if the capacitor is capable of doing a rapid charge and discharge (like your lungs, it kind of has to breathe deeply) to eliminate random dropouts, and you cannot see double sparks.