### Question:
Minion implements MessageListener<CoreMessage>, Codable, AutoCloseable { protected void joinGroup() { minionGroupMembership = new ZkGroupMembership(getZkClient(), true); String upPath = MINION_ZK_PATH + "up"; try { if (zkClient.checkExists().forPath(upPath) == null) { zkClient.create().creatingParentsIfNeeded().forPath(upPath, null); } } catch (KeeperException.NodeExistsException e) { } catch (Exception e) { log.error("Exception joining group", e); } log.info("joining group: {}", upPath); minionGroupMembership.addToGroup(upPath, getUUID(), shutdown); } @VisibleForTesting  Minion(CuratorFramework zkClient); @JsonCreator private  Minion(@JsonProperty("dataDir") File rootDir,
                   @Nullable @JsonProperty("queueType") String queueType,
                   @Nullable @JsonProperty("hostLocationInitializer") HostLocationInitializer hostLocationInitializer); static void main(String[] args); File getRootDir(); void setDiskReadOnly(boolean disk_read_only); @VisibleForTesting void insertJobKickMessage(CommandTaskKick kick); @Override void onMessage(CoreMessage message); void sendHostStatus(); String getUUID(); boolean getShutdown(); @Override void close(); static final String MINION_ZK_PATH; static final String batchJobQueueSuffix; static final String batchControlQueueSuffix; static final Meter tasksCompletedPerHour; }### Answer:
@Test public void testJoinGroup() throws Exception { Minion minion = new Minion(zkClient); minion.joinGroup(); List<String> upMinions = zkClient.getChildren().forPath("/minion/up"); assertEquals(ImmutableList.of(minion.getUUID()), upMinions); minion.closeZkClient(); }