Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance

Measurement:

Inspect the spark electrodes for good overall condition i.e. clean, no cracked ceramic and not warped.
Measure the resistance across each of the spark electrodes, expect continuity/zero resistance.
Check the spark gap between the two ignition electrodes is approximately 4mm.
Note:
Electrode assembly must be refitted with a new gasket on reassembly.