### Question:
BackupNode extends NameNode { BackupNode(Configuration conf, NamenodeRole role) throws IOException { super(conf, role); } BackupNode(Configuration conf, NamenodeRole role); @Override // NameNode void stop(); boolean setSafeMode(SafeModeAction action);  }### Answer:
@Test public void testBackupNode() throws Exception { testCheckpoint(StartupOption.BACKUP); }