That's what sucks about coils for our car ... They can bench test fine and still fail when they're on the car.
Temperature, humidity, engine load, whatever, they just fail when they feel like it.... And not necessarily enough to throw an engine mis-fire code.
And,.. an engine misfire is the only code that flashes the MIL on our car... You can fry your pre-cat in a couple of minutes if raw gas is dumped on it... A $1,200-1,4000 job if OEM parts are used.
In California, OEM parts must be used for any emission related repair.
So Yea... There's a test for our coils, and if they test bad then they're definitely bad, BUT they may be crap even if they test fine.
They can even be crap brand new outta the box... But still test fine...
So here's the bench test... (make sure your bench is hot, humid and shaking a lot)