Set Appliance State:

Gas Off
Isolate Mains Power to appliance as per TOPs P4
CH Demand
Removing combustion door
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset appliance as necessary.
After approx. 24 seconds can sparking be seen at the ignition electrode?
Note:
Spark should be visible when viewing from slightly below inner combustion cover. If in doubt or access is poor remove inner combustion cover to view.