[Nix-dev] NixOS configuration unit tests

[Eelco Dolstra]

Hi,

On 23/01/15 15:04, Wout Mertens wrote:

> I'm thinking that it might be a good idea to have unit tests for the
> configuration.nix descriptions. That way we can be more sure that a change
> doesn't have unintended consequences.
> 
> For example, we could have tests like "if you set config.foo and config.bar, the
> evaluation should fail" and "if you set config.foo then config.baz should get a
> value".
> 
> One specific use case is the license whitelisting/blacklisting
> (https://github.com/NixOS/nixpkgs/pull/5892), where we don't ever want to
> inadvertently allow forbidden licenses.
> 
> Any thoughts on how to implement this? An approach might be a shell script that
> runs a few nix-instantiate command lines and expects errors and values, but how
> would that integrate with the nixos tests?

Basically by adding a job like this to nixos/release.nix (not tested):

  bla = runCommand "bla"
    { buildInputs = [ nix ];
      src = ./..;
    }
    ''
      # Ugly hack to make read-only evaluation work.
      export NIX_DB_DIR=$TMPDIR
      export NIX_STATE_DIR=$TMPDIR
      nix-store --init

      echo '{ config.foo = true; config.bar = true; }' > foo.nix
      nix-instantiate --dry-run $src/nixos -A system \
        -I nixos-configuration=$(pwd)/foo.nix
      ...
    '';

and then add this job to "tested" in nixos/release-combined.nix to make the
NixOS channel depend on it.

-- 
Eelco Dolstra | LogicBlox, Inc. | http://nixos.org/~eelco/