Set Appliance State:

Mains Power Off
Turn Hot Water Tap On
C/H Demand OFF
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Allow burner to ignite and establish.
Use appliance isolation tap to isolate water while observing flame through sight glass.
Flame should extinguish within 1 second.
If any beads of flame remain this would indicate a passing gas valve.