You can now run a test in the nixos/tests directory directly using
nix-build, e.g.
$ nix-build '<nixos/tests/login.nix>' -A test
This gets rid of having to add the test to nixos/tests/default.nix.
(Of course, you still need to add it to nixos/release.nix if you want
Hydra to run the test.)
Now that overriding fileSystems in qemu-vm.nix works again, it's
important that the VM tests that add additional file systems use the
same override priority. Instead of using the same magic constant
everywhere, they can now use mkVMOverride.
http://hydra.nixos.org/build/6695561
