@Test
  public void testDisableBackupDir() throws IOException {
    helixConfigProps.remove(HelixAccountServiceConfig.BACKUP_DIRECTORY_KEY);
    VerifiableProperties vHelixConfigProps = new VerifiableProperties(helixConfigProps);
    HelixAccountServiceConfig config = new HelixAccountServiceConfig(vHelixConfigProps);
    BackupFileManager backup =
        new BackupFileManager(accountServiceMetrics, config.backupDir, config.maxBackupFileCount);

    // getLatestAccounts should return null
    assertNull("Disabled backup shouldn't have any state", backup.getLatestAccounts(0));

    // persistAccountMap should not create any backup
    Stat stat = new Stat();
    stat.setVersion(1);
    stat.setMtime(System.currentTimeMillis());

    backup.persistAccountMap(Collections.emptyList(), stat.getVersion(), stat.getMtime() / 1000);
    assertTrue("Disabled backup shouldn't add any backup", backup.isEmpty());
  }
Test disable backup. Every method from {@link BackupFileManager} should return null or have no effect.
@throws IOException if I/O error occurs
ambry-account/src/test/java/com/github/ambry/account/BackupFileManagerTest.java