home-manager/tests/modules/systemd/services.nix

{ pkgs, ... }:

let
  drvScript = pkgs.writeShellScript "drv-script.sh" ''
    echo "Just a test"
  '';
in {
  config = {
    systemd.user.services."test-service@" = {
      Unit = { Description = "A basic test service"; };

      Service = {
        Environment = [ "VAR1=1" "VAR2=2" ];
        ExecStartPre = drvScript;
        ExecStart = ''/some/exec/start/command --with-arguments "%i"'';
      };
    };

    nmt.script = ''
      serviceFile=home-files/.config/systemd/user/test-service@.service
      assertFileExists $serviceFile
      assertFileContent $serviceFile \
        ${
          pkgs.writeText "services-expected.conf" ''
            [Service]
            Environment=VAR1=1
            Environment=VAR2=2
            ExecStart=/some/exec/start/command --with-arguments "%i"
            ExecStartPre=${drvScript}

            [Unit]
            Description=A basic test service
          ''
        }
    '';
  };
}