Hi @milnejames, good morning. Thanks for reaching out.
To voltage test on the Iro, your landscaper would need to do this at each valve as the Iro requires the front panel to be connected to the wall mount for electricity to pass from the front panel (which is connected to the power adaptor) and out to the wires via the wallmount.
Some landscapers have simply taken a short length of sprinkler wire, connected it to the terminals in the wall mount, and tested voltage at the controller's location by bypassing the need to wire up all of the zones. Others have installed a terminal strip below the Iro to connect the short length of sprinkler wire into, then connect the valve wires into the terminal strip so they could test the voltage easily at a later date. This also works well for larger gauge wiring if you're concerned about space within the Iro's wallmount.
Hope this helps