public Set<String> assembleAllWatchKeys(String appId, String clusterName, String namespace,
                                          String dataCenter) {
    Multimap<String, String> watchedKeysMap =
        assembleAllWatchKeys(appId, clusterName, Sets.newHashSet(namespace), dataCenter);
    return Sets.newHashSet(watchedKeysMap.get(namespace));
  }
@Test
  public void testAssembleWatchKeysForNoAppIdPlaceHolder() throws Exception {
    Multimap<String, String> watchKeysMap =
        watchKeysUtil.assembleAllWatchKeys(ConfigConsts.NO_APPID_PLACEHOLDER, someCluster,
            Sets.newHashSet(someNamespace, anotherNamespace), someDC);

    assertTrue(watchKeysMap.isEmpty());
  }