WTB Nissan Cefiro A32 meter panel

got a question, how we can know whether our spark plug had better ignition after we add on something like better ignition coil / spark booster?

i saw in carrefour there's a small device to let customer to see how the spark like after add the extra things...so how we goonna test it in car? can we just take out 1 spark plug and see how it fire?

maybe a bit silly but i think this is the best way to prove whether the booster things we added are useful or not...