### Question:
OMFailoverProxyProvider implements
    FailoverProxyProvider<OzoneManagerProtocolPB>, Closeable { public Text getCurrentProxyDelegationToken() { return delegationTokenService; } OMFailoverProxyProvider(ConfigurationSource configuration,
      UserGroupInformation ugi, String omServiceId); @VisibleForTesting synchronized String getCurrentProxyOMNodeId(); @Override synchronized ProxyInfo getProxy(); @VisibleForTesting RetryPolicy getRetryPolicy(int maxFailovers); Text getCurrentProxyDelegationToken(); @Override Class<OzoneManagerProtocolPB> getInterface(); @Override void performFailover(OzoneManagerProtocolPB currentProxy); void performFailoverIfRequired(String newLeaderOMNodeId); void performFailoverToNextProxy(); synchronized long getWaitTime(); synchronized boolean shouldFailover(Exception ex); @Override synchronized void close(); @VisibleForTesting List<ProxyInfo> getOMProxies(); @VisibleForTesting Map<String, ProxyInfo<OzoneManagerProtocolPB>> getOMProxyMap(); @VisibleForTesting List<OMProxyInfo> getOMProxyInfos(); static OMNotLeaderException getNotLeaderException(
      Exception exception); static final Logger LOG; }### Answer:
@Test public void testCanonicalTokenServiceName() throws IOException { OzoneConfiguration ozoneConf = new OzoneConfiguration(); ArrayList<String> nodeAddrs = new ArrayList<>( Arrays.asList("4.3.2.1:9862", "2.1.0.5:9862", "3.2.1.0:9862")); Assert.assertEquals(numNodes, nodeAddrs.size()); StringJoiner allNodeIds = new StringJoiner(","); for (int i = 1; i <= numNodes; i++) { String nodeId = NODE_ID_BASE_STR + i; ozoneConf.set(OmUtils.addKeySuffixes(OZONE_OM_ADDRESS_KEY, OM_SERVICE_ID, nodeId), nodeAddrs.get(i-1)); allNodeIds.add(nodeId); } ozoneConf.set(OmUtils.addKeySuffixes(OZONE_OM_NODES_KEY, OM_SERVICE_ID), allNodeIds.toString()); OMFailoverProxyProvider prov = new OMFailoverProxyProvider(ozoneConf, UserGroupInformation.getCurrentUser(), OM_SERVICE_ID); Text dtService = prov.getCurrentProxyDelegationToken(); Collections.sort(nodeAddrs); String expectedDtService = String.join(",", nodeAddrs); Assert.assertEquals(expectedDtService, dtService.toString()); }