public LogAggregationFileController getFileControllerForWrite() {
    return controllers.getFirst();
  }
@Test
  void testDefaultConfUsed() {
    Configuration conf = getConf();
    conf.unset(YarnConfiguration.NM_REMOTE_APP_LOG_DIR);
    conf.unset(YarnConfiguration.NM_REMOTE_APP_LOG_DIR_SUFFIX);
    conf.set(LOG_AGGREGATION_FILE_FORMATS, "TFile");

    LogAggregationFileControllerFactory factory =
        new LogAggregationFileControllerFactory(getConf());
    LogAggregationFileController fc = factory.getFileControllerForWrite();

    assertEquals("/tmp/logs",
        fc.getRemoteRootLogDir().toString(),
        WRONG_ROOT_LOG_DIR_MSG);
    assertEquals("logs-tfile",
        fc.getRemoteRootLogDirSuffix(),
        WRONG_ROOT_LOG_DIR_SUFFIX_MSG);
  }