error: attribute 'services' missing

[milahu]

cd nix-gui
nix develop
cd nixui
p=/nix/store/ip17r412b9by9nwb0ri0avrzhvv49ajc-source
export NIX_PATH=$p:nixpkgs=$p:nixos-config=$(readlink -f tests/sample/configuration.nix)
pytest -svv tests/test_api.py::test_get_option_tree

E               nixui.options.nix_eval.NixEvalError: NixEvalError("""
E               error: attribute 'services' missing
E               
E                      at /tmp/nix-gui/nixui/tests/sample/configuration.nix:95:25:
E               
E                          94|         # test getting config
E                          95|         echo ${toString config.services.nix-serve.port}
E                            |                         ^
E                          96|       '';