GitOrigin-RevId: 988cc958c57ce4350ec248d2d53087777f9e1949
2.6 KiB
Developing the NixOS Test Driver
The NixOS test framework is a project of its own.
It consists of roughly the following components:
nixos/lib/test-driver
: The Python framework that sets up the test and runs thetestScript
nixos/lib/testing
: The Nix code responsible for the wiring, written using the (NixOS) Module System.
These components are exposed publicly through:
nixos/lib/default.nix
: The public interface that exposes thenixos/lib/testing
entrypoint.flake.nix
: Exposes thelib.nixos
, including the public test interface.
Beyond the test driver itself, its integration into NixOS and Nixpkgs is important.
pkgs/top-level/all-packages.nix
: Defines thenixosTests
attribute, used by the packagetests
attributes and OfBorg.nixos/release.nix
: Defines thetests
attribute built by Hydra, independently, but analogous tonixosTests
nixos/release-combined.nix
: Defines which tests are channel blockers.
Finally, we have legacy entrypoints that users should move away from, but are cared for on a best effort basis.
These include pkgs.nixosTest
, testing-python.nix
and make-test-python.nix
.
Testing changes to the test framework
When making significant changes to the test framework, we run the tests on Hydra, to avoid disrupting the larger NixOS project.
For this, we use the python-test-refactoring
branch in the NixOS/nixpkgs
repository, and its corresponding Hydra jobset.
This branch is used as a pointer, and not as a feature branch.
- Rebase the PR onto a recent, good evaluation of
nixos-unstable
- Create a baseline evaluation by force-pushing this revision of
nixos-unstable
topython-test-refactoring
. - Note the evaluation number (we'll call it
<previous>
) - Push the PR to
python-test-refactoring
and evaluate the PR on Hydra - Create a comparison URL by navigating to the latest build of the PR and adding to the URL
?compare=<previous>
. This is not necessary for the evaluation that comes right after the baseline.
Review the removed tests and newly failed tests using the constructed URL; otherwise you will accidentally compare iterations of the PR instead of changes to the PR base.
As we currently have some flaky tests, newly failing tests are expected, but should be reviewed to make sure that
- The number of failures did not increase significantly.
- All failures that do occur can reasonably be assumed to fail for a different reason than the changes.