### Question:
ZKUtil { public static void updateIfExists(String zkAddress, String path, final ZNRecord record, boolean mergeOnUpdate) { RealmAwareZkClient zkClient = getHelixZkClient(zkAddress); try { updateIfExists(zkClient, path, record, mergeOnUpdate); } finally { zkClient.close(); } } private  ZKUtil(); static boolean isClusterSetup(String clusterName, String zkAddress); static boolean isClusterSetup(String clusterName, RealmAwareZkClient zkClient); static boolean isInstanceSetup(String zkAddress, String clusterName, String instanceName,
      InstanceType type); static boolean isInstanceSetup(RealmAwareZkClient zkclient, String clusterName,
      String instanceName, InstanceType type); static void createChildren(String zkAddress, String parentPath, List<ZNRecord> list); static void createChildren(RealmAwareZkClient client, String parentPath,
      List<ZNRecord> list); static void createChildren(String zkAddress, String parentPath, ZNRecord nodeRecord); static void createChildren(RealmAwareZkClient client, String parentPath,
      ZNRecord nodeRecord); static void dropChildren(String zkAddress, String parentPath, List<ZNRecord> list); static void dropChildren(RealmAwareZkClient client, String parentPath,
      List<ZNRecord> list); static void dropChildren(String zkAddress, String parentPath, ZNRecord nodeRecord); static void dropChildren(RealmAwareZkClient client, String parentPath,
      ZNRecord nodeRecord); static List<ZNRecord> getChildren(String zkAddress, String path); static List<ZNRecord> getChildren(RealmAwareZkClient client, String path); static void updateIfExists(String zkAddress, String path, final ZNRecord record,
      boolean mergeOnUpdate); static void updateIfExists(RealmAwareZkClient client, String path, final ZNRecord record,
      boolean mergeOnUpdate); static void createOrMerge(String zkAddress, String path, final ZNRecord record,
      final boolean persistent, final boolean mergeOnUpdate); static void createOrMerge(RealmAwareZkClient client, String path, final ZNRecord record,
      final boolean persistent, final boolean mergeOnUpdate); static void createOrUpdate(String zkAddress, String path, final ZNRecord record,
      final boolean persistent, final boolean mergeOnUpdate); static void createOrUpdate(RealmAwareZkClient client, String path, final ZNRecord record,
      final boolean persistent, final boolean mergeOnUpdate); static void asyncCreateOrMerge(String zkAddress, String path, final ZNRecord record,
      final boolean persistent, final boolean mergeOnUpdate); static void asyncCreateOrMerge(RealmAwareZkClient client, String path,
      final ZNRecord record, final boolean persistent, final boolean mergeOnUpdate); static void createOrReplace(String zkAddress, String path, final ZNRecord record,
      final boolean persistent); static void createOrReplace(RealmAwareZkClient client, String path, final ZNRecord record,
      final boolean persistent); static void subtract(String zkAddress, final String path,
      final ZNRecord recordTosubtract); static void subtract(RealmAwareZkClient client, final String path,
      final ZNRecord recordTosubtract); static String toHexSessionId(long sessionId); static Map<String, String> fromStatToMap(Stat stat);  }### Answer:
@Test() public void testUpdateIfExists() { String path = PropertyPathBuilder.instanceConfig(clusterName, "id3"); ZNRecord record = new ZNRecord("id4"); ZKUtil.updateIfExists(_gZkClient, path, record, false); AssertJUnit.assertFalse(_gZkClient.exists(path)); _gZkClient.createPersistent(path); ZKUtil.updateIfExists(_gZkClient, path, record, false); AssertJUnit.assertTrue(_gZkClient.exists(path)); record = _gZkClient.readData(path); AssertJUnit.assertEquals("id4", record.getId()); }