Set Appliance State:

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

Measurement:

Measure the resistance across the ignition lead from the PCB connector to the ignition electrode connector.
Expect continuity / zero resistance.
Inspect the lead for good overall condition, checking there is no damaged insulation and that the connectors are a tight fit.
Are the harness checks satisfactory?