Can I allow multiple user accounts to open applications directly onto one MacOS desktop?
On X Windows, it's typically about setting DISPLAY and XAUTH. I suspect it's impossible on native MacOS, but it seems worth asking.
I know I can have several users on a single Mac, each running a separate desktop.
I know I can even use ScreenSharing with an SSH tunnel to have those other users' desktops visible on my primary desktop.
The background: I can run (calabash) tests across multiple iOS simulators on one machine at once, each as a different user to provide process/admin separation, each to that user's desktop (using parallel_calabash) but running several desktops wastes machine resources that would be much better spent running more simulators.
Seems the answer is no.
As of ElCapitan in particular, Apple's security model even makes it difficult/impossible to interact with the desktop from an ssh session to the same user on the same machine, unless you run an sshd from that user's Desktop context such as with a ~/Library/LaunchAgent.