Spark Plug Test

Remove the spark plug and connect to the ignition coil.
Ground the spark plug outer electrode (body), and crank the engine.
Check that there is an electrical discharge between the electrodes at this time.

Fig 1: Removing Spark Plug
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

Fig 2: Checking Electrical Discharge Between Electrodes
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.