Surely you'd want CI builds for your app? I suppose you can always go the sassy option and just offload this problem onto Travis or CircleCI, but then they're the ones stuck figuring out how to rack thousands of Mac Minis, dealing with thermals in a machine that isn't set up for hot/cold aisles, a computer that doesn't have a serial port or dedicated management interface, etc.

If you're a big enough org or the app is for internal use, this might not be an option anyway. At that point I imagine most people just give up on it and figure out how to run macOS on a generic VM. But at that point you have to convince your IT department that it's worth it doing a thing that is definitely unsupported and in violation of the TOS.

Or maybe some of these are big enough that they are able to approach Apple and get a special license for N concurrent instances of macOS running on virtualized hardware? Who knows.