Set Appliance State:

Turn Hot Water Tap On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Allow the boiler to run in DHW mode.
Turn the hot water tap off.
Does the burner extinguish as soon as the tap is turned off?
Note:
If the tap is not located near the appliance the isolation valve underneath the appliance can be used to turn the water off instead.