anchor.diff:              ok = erl_tar:create(Tarball,
                                   [{"contents.tar.gz", Contents}],
                                   []),
  -            [file:delete(F) || F <- Files],
  -            {tarball, Tarball}
  +            Cache = proplists:get_value(cache_dir, Opts, filename:join(Dir,"cache")),
  +            Cached = filename:join([Cache, TarApp]),
  +            filelib:ensure_dir(Cached),
  +            rebar_file_utils:mv(Tarball, Cached),
  +            {ok, true}
           end).
   
   %% @doc On top of the pkg resource mocking, we need to mock the package
  
positive.code: -spec mock(Opts) -> ok when
      Opts :: [Option],
      Option :: {update, [App]}
              | {default_vsn, Vsn}
              | {override_vsn, [{App, Vsn}]}
              | {not_in_index, [{App, Vsn}]}
  
negative.code:                 [kernel, stdlib] ++ [element(1,D) || D  <- AppDeps]
              ),
              rebar_test_utils:create_config(Dir, [{deps, AppDeps}]),
              TarApp = App++"-"++binary_to_list(Vsn)++".tar",
              Tarball = filename:join([Dir, TarApp]),
              Contents = filename:join([Dir, "contents.tar.gz"]),
              Files = all_files(rebar_app_info:dir(AppInfo)),
              ok = erl_tar:create(Contents,
  