Set Appliance State:

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

Observation:

Does the pump run continuously for longer than 5 seconds?
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 that water does not run onto the electrics.