Set Appliance State:

Set Multimeter to AC Volts Set meter to measure AC Volts
CH Demand
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the AC voltage between the switch live supply (second terminal down) and neutral at the incoming mains supply terminals.
Expect mains voltage.
Is the voltage measured as expected?