{ busybox }:
with import "${builtins.getEnv "_NIX_TEST_BUILD_DIR"}/config.nix";
let

  mkDerivation = args:
    derivation ({
      inherit system;
      builder = busybox;
      args = ["sh" "-e" args.builder or (builtins.toFile "builder-${args.name}.sh" ''
        if [ -e "$NIX_ATTRS_SH_FILE" ]; then source $NIX_ATTRS_SH_FILE; fi;
        eval "$buildCommand"
      '')];
    } // removeAttrs args ["builder" "meta"])
    // { meta = args.meta or {}; };
in
{

  failing = mkDerivation {
    name = "failing";
    buildCommand = ''
      echo foo > bar
      exit 1
    '';
  };
}