Set Appliance State:

Gas Off
Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
Remove ignition lead from spark generator and make safe
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset appliance if required.
Approximately 4 seconds after the fan has started a strong consistent spark should be seen between the spark generator output terminal and the PCB earth connection.
This will occur five times before ignition lockout occurs.
Is there a strong consistent spark?
Note.
Reset appliance as required until test is complete.