Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
When removing the electrode take care not to distort or bend the electrode tip

Measurement:

Remove and inspect ignition electrode and its lead for general condition.
Thoroughly check the ceramic for damage and ensure the electrode is not distorted.
Check the electrode and lead for resistance.
Expected resistance 1 kOhms.