Use Niv to pin nixpkgs
To run the tests, channels are used. Since channels evolve, we are not able to reproduce locally a CI job. It is also not convenient to run these jobs. I think it would be more stable to pin the nixpkgs version used by the tests.
I'm going to use Niv to pin several nixpkgs version and add a default.nix in the tests directory use the attributes: intern.19.09
, intern.unstable
, extern.19.09
, extern.unstable
...
Latter, we could add a scheduled job to run niv to update nixpkgs versions and create PRs.
WDYT?