Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
Selector Switch in HOT WATER position.
Connect a U-Gauge to the Gas Valve outlet pressure test point.
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Does the U-Gauge indicate a positive gas pressure?
Isolate Mains Power to appliance
as per TOP's P4
Note: When U-gauge is removed pressure test point should be tightened & checked for gas soundness.