anchor.diff:      ExternalFileId = <<"external_file_id">>,
   
       % create test file
  -    {ok, FileUuid} = lfm_proxy:create(W1, SessionId, <<"test_file">>, 8#777),
  -    {ok, Handle} = lfm_proxy:open(W1, SessionId, {uuid, FileUuid}, rdwr),
  +    {ok, FileGUID} = lfm_proxy:create(W1, SessionId, <<"test_file">>, 8#777),
  +    FileUuid = fslogic_uuid:file_guid_to_uuid(FileGUID),
  +    {ok, Handle} = lfm_proxy:open(W1, SessionId, {guid, FileGUID}, rdwr),
       ?assertMatch({ok, 10}, lfm_proxy:write(W1, Handle, 0, <<"0123456789">>)),
       ?assertMatch(ok, lfm_proxy:fsync(W1, Handle)),
   
  
positive.code: truncate_should_change_size_and_blocks(Config) ->
      [W1 | _] = ?config(op_worker_nodes, Config),
      SessionId = <<"session_id1">>,
      {ok, FileUuid} = lfm_proxy:create(W1, SessionId, <<"test_file">>, 8#777),
      {ok, Handle} = lfm_proxy:open(W1, SessionId, {uuid, FileUuid}, rdwr),
      ?assertMatch({ok, 10}, lfm_proxy:write(W1, Handle, 0, <<"0123456789">>)),
  
      %when
      ?assertMatch(ok, lfm_proxy:truncate(W1, SessionId, {uuid, FileUuid}, 6)),
      ?assertMatch(ok, lfm_proxy:fsync(W1, Handle)),
  
      %then
  
negative.code:     ExternalProviderId = <<"external_provider_id">>,
      ExternalFileId = <<"external_file_id">>,
      ExternalBlocks = [#file_block{offset = 0, size = 10, file_id = ExternalFileId, storage_id = <<"external_storage_id">>}],
      {ok, FileGUID} = lfm_proxy:create(W1, SessionId, <<"test_file">>, 8#777),
      FileUuid = fslogic_uuid:file_guid_to_uuid(FileGUID),
      {ok, Handle} = lfm_proxy:open(W1, SessionId, {guid, FileGUID}, rdwr),
      ?assertMatch({ok, 10}, lfm_proxy:write(W1, Handle, 0, <<"0123456789">>)),
      ?assertMatch(ok, lfm_proxy:fsync(W1, Handle)),
      RemoteLocation = #file_location{size = 10, space_uuid = SpaceId,
  