Set Appliance State:

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

Observation:

Allow pump to start Switch off boiler.
Does the pump stop quickly (i.e. within a second or two)?
Note:
Do not take noise or vibration as evidence of pump running.
If vent plug is removed to ascertain pump running then precautions must be taken to catch water that will escape and ensure water does not run onto the electrics.