Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove rectification electrode from burner (left electrode)

Measurement:

Check spark electrode is in good overall condition, ceramic uncracked and not warped or distorted.
Check for continuity (zero resistance) between the tip of the electrode to the lead connection.
Note:
If unsure about condition of electrode remove the spark electrode and compare - they should be identical.