Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
ON/OFF switch set to ON (button pushed in)

Measurement:

Test 1:
Measure the resistance across the top two wires of the ON/OFF switch (blue and black).
Resistance should be short circuit (zero resistance).
Test 2:
Measure the resistance across the bottom two wires of the ON/OFF switch (brown and black).
Resistance should be short circuit (zero resistance).