My friend asked to find and fix their gas leak. Must be an excuse to buy a new tool then. I could have achieved the same results with just the soapy water. Gas leak detector - amzn.to/3Fnxliz
I'm sure the tester has its place. But I still check with soapy water. And it did narrow down the area of the leak before I had to pull the hob and sink up. The repair was a very dull tightening of the slack connector (most likely heat cycled) and then a spray with soapy water to confirm no more leak.