This creates and uses a function named mkNixinateTest which takes a
buildOn argument. This expects to be either "local" or "remote". This
means we can make a test for both use cases of Nixinate. One where we
build on the remote machine, and one where we build locally and push to
the remote machine. These tests are then added to the top level of the
tests folder and are imported by the flake.nix
This initializes ./test/default.nix which is referred to by the
flake.nix under the `checks` attribute. This default.nix should point to
all future tests, where they can be looked up and ran like:
nix build .#checks.x86_64-linux.vmTest
The test included is a simple NixOS VM Test. It uses Nixinate to deploy
a machine with `services.nginx.enable = true` set, and tests whether
nginx.service is started and reachable after deployment.
