@VisibleForTesting
  BackupReplayFile openOrCreateReplayFile() {
    try {
      final Optional<BackupReplayFile> backupReplayFile = latestReplayFile();
      if (backupReplayFile.isPresent()) {
        return backupReplayFile.get();
      }
      return newReplayFile();
    } catch (final IOException e) {
      throw new RuntimeException(e);
    }
  }
@Test
  public void shouldCreateNewReplayFileWhenNoBackupFilesExist() {
    // Given:
    when(ticker.get()).thenReturn(123L);

    // When:
    final BackupReplayFile replayFile = commandTopicBackup.openOrCreateReplayFile();

    // Then:
    assertThat(replayFile.getPath(), is(String.format(
        "%s/backup_command_topic_123", backupLocation.getRoot().getAbsolutePath()
    )));
  }