Set Appliance State:

Mains Power Off
Turn Hot Water Tap On
Selector switch to hot water position
CH temperature selector to minimum
DHW temperature selector to maximum
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Allow ignition sequence to commence.
Observe through the inspection window.
Does the pilot ignite?
Is the flame picture satisfactory on both sides of the pilot?