Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove lower facia panel
Disconnect the plug from the gas valve

Measurement:

Test 1:
Measure the resistance between the top and bottom pins of the gas valve.
Resistance should be approximately 3.7kOhms.
Test 2:
Measure the resistance between the top pin of
the gas valve to a suitable earth point.
Resistance should be greater than 1M Ohm.