nixpkgs/nixos/lib/testing/run.nix

{ config, hostPkgs, lib, ... }:
let
  inherit (lib) types mkOption;
in
{
  options = {
    passthru = mkOption {
      type = types.lazyAttrsOf types.raw;
      description = ''
        Attributes to add to the returned derivations,
        which are not necessarily part of the build.

        This is a bit like doing `drv // { myAttr = true; }` (which would be lost by `overrideAttrs`).
        It does not change the actual derivation, but adds the attribute nonetheless, so that
        consumers of what would be `drv` have more information.
      '';
    };

    rawTestDerivation = mkOption {
      type = types.package;
      description = ''
        Unfiltered version of `test`, for troubleshooting the test framework and `testBuildFailure` in the test framework's test suite.
        This is not intended for general use. Use `test` instead.
      '';
      internal = true;
    };

    test = mkOption {
      type = types.package;
      # TODO: can the interactive driver be configured to access the network?
      description = ''
        Derivation that runs the test as its "build" process.

        This implies that NixOS tests run isolated from the network, making them
        more dependable.
      '';
    };
  };

  config = {
    rawTestDerivation = hostPkgs.stdenv.mkDerivation {
      name = "vm-test-run-${config.name}";

      requiredSystemFeatures = [ "nixos-test" ]
        ++ lib.optionals hostPkgs.stdenv.hostPlatform.isLinux [ "kvm" ]
        ++ lib.optionals hostPkgs.stdenv.hostPlatform.isDarwin [ "apple-virt" ];

      buildCommand = ''
        mkdir -p $out

        # effectively mute the XMLLogger
        export LOGFILE=/dev/null

        ${config.driver}/bin/nixos-test-driver -o $out
      '';

      passthru = config.passthru;

      meta = config.meta;
    };
    test = lib.lazyDerivation { # lazyDerivation improves performance when only passthru items and/or meta are used.
      derivation = config.rawTestDerivation;
      inherit (config) passthru meta;
    };

    # useful for inspection (debugging / exploration)
    passthru.config = config;
  };
}