Set Appliance State:

Gas Off
Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
Remove burner insulation cover
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Confirm the spark gap is 3.0 - 4.0 mm and sparking in correct place.
Spark should be to the burner rail.