Now you can just say:
$ nix-build '<nixos/tests/login.nix>'
You can still get the driver script for interactive testing:
$ nix-build '<nixos/tests/login.nix>' -A driver
$ ./result/bin/nixos-test-driver
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.)
It's now "<yy>.<mm>pre<commit-count>.<short-hash>"
(e.g. "13.10pre5678.gfedcba") for the unstable branch, and
"<yy>.<mm>.<commit-count>.<short-hash>" (e.g. "13.10.5678.gfedcba")
for stable branches.