Ring around a few plumbers. Some will only do a full test and service but I found a bigger company who would just do the check. Decided to wait until the beginning of winter though
Most gas fitters/plumbers will do the test. Legally they have to test all gas appliances when working on them due to the unfortunate deaths due to carbon monoxide poisoning. If the unit hasn't been serviced for a while I would get it serviced which includes the test anyway.
It's usually the internal gas wall furnaces that are the most problematic.
If it's a new unit you should be right for a couple of years.
Regardless the test shouldn't cost you more than a tradie call out fee which includes 15-30 minutes of labour so most will do a semi service/check as the test really only takes 5-10 minutes using an electric meter.
