Set Appliance State:

Set Multimeter to AC Voltage Set meter to measure AC Volts
Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
CH Selector Switch Off
Gas Control Knob in Main Burner position
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the voltage across the Gas Valve Solenoid Coil connections (Purple wires) at the Gas Valve. This voltage should be greater than 16V AC.