anchor.diff:  
       run_tests(W, #test_spec{
           root_dir = atom_to_binary(?FUNCTION_NAME, utf8),
  -%%        requires_traverse_ancestors = false,
  -        files = [#file{
  -            name = <<"file1">>,
  -            perms = [?read_object]
  +        files = [#file{
  +            name = <<"file1">>,
  +            perms = [?read_object],
  +            on_create = fun(OwnerSessId, Guid) ->
  +                % write to file to force its creation on storage. Otherwise it
  +                % may be not possible during tests without necessary perms.
  +                fill_file_with_dummy_data(W, OwnerSessId, Guid),
  +                Guid
  +            end
           }],
           operation = fun(_OwnerSessId, SessId, TestCaseRootDirPath, ExtraData) ->
               FilePath = <<TestCaseRootDirPath/binary, "/file1">>,
  
positive.code:         rm_dir_test,
  
          create_file_test,
  %%        open_for_read_test,       % TODO uncomment after fixing
  %%        open_for_write_test,
  %%        open_for_rdwr_test,
          create_and_open_test,
          truncate_test,
          mv_file_test,
  
negative.code:         root_dir = atom_to_binary(?FUNCTION_NAME, utf8),
          files = [#file{
              name = <<"file1">>,
              perms = [?read_object, ?write_object],
              on_create = fun(OwnerSessId, Guid) ->
                  % write to file to force its creation on storage. Otherwise it
                  % may be not possible during tests without necessary perms.
                  fill_file_with_dummy_data(W, OwnerSessId, Guid),
                  Guid
              end
          }],
          operation = fun(_OwnerSessId, SessId, TestCaseRootDirPath, ExtraData) ->
              FilePath = <<TestCaseRootDirPath/binary, "/file1">>,
  