Justine here. I have a fleet of VMs for various OSes running the runitd.com daemon. I then write unit tests in Emacs and when I press CTRL-C CTRL-_ it builds the test, gzips it, and uses runit.com to deploy and run the executable to every VM, and reports back the output within milliseconds. Here's a screenshot of me testing the sendfile() system call: https://justine.lol/cosmopolitan/sendfile-testing.png When I run `make test` it deploys and runs all 465 test executables to all seven test VMs currently in the fleet, and it takes about 10 seconds. Here's a video: https://storage.googleapis.com/justine/sizetricks/runit.mp4 All runit.com and runitd.com do (their sources are in tool/build/ of the cosmo github repo) is basically `scp program host: && ssh host ./program` which is what I used to do, except SSH was unacceptably slow, so I wrote runit, which use PSK TLS and DEFLATE to transfer files over the network.