Set Appliance State:

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

Measurement:

Test 1:
Measure the resistance across the top and bottom pins of the gas valve.
Expect a resistance of approximately 55 ohms.
Test 2:
Measure the resistance between the top pin and a suitable earth.
Expect a resistance of 1Mohm or greater.
(O.L is acceptable because it is greater than 1Mohm)