### Question:
CommandUtil { public static Map<String, List<String>> fetchMasterAndSlaveDistinguish( final MQAdminExt adminExt, final String clusterName) throws InterruptedException, RemotingConnectException, RemotingTimeoutException, RemotingSendRequestException, MQBrokerException { Map<String, List<String>> masterAndSlaveMap = new HashMap<String, List<String>>(4); ClusterInfo clusterInfoSerializeWrapper = adminExt.examineBrokerClusterInfo(); Set<String> brokerNameSet = clusterInfoSerializeWrapper.getClusterAddrTable().get(clusterName); if (brokerNameSet == null) { System.out .printf("[error] Make sure the specified clusterName exists or the nameserver which connected is correct."); return masterAndSlaveMap; } for (String brokerName : brokerNameSet) { BrokerData brokerData = clusterInfoSerializeWrapper.getBrokerAddrTable().get(brokerName); if (brokerData == null || brokerData.getBrokerAddrs() == null) { continue; } String masterAddr = brokerData.getBrokerAddrs().get(MixAll.MASTER_ID); masterAndSlaveMap.put(masterAddr, new ArrayList<String>()); for (Long id : brokerData.getBrokerAddrs().keySet()) { if (brokerData.getBrokerAddrs().get(id) == null || id.longValue() == MixAll.MASTER_ID) { continue; } masterAndSlaveMap.get(masterAddr).add(brokerData.getBrokerAddrs().get(id)); } } return masterAndSlaveMap; }  static Map<String/*master addr*/, List<String>/*slave addr*/> fetchMasterAndSlaveDistinguish(
        final MQAdminExt adminExt, final String clusterName); static Set<String> fetchMasterAddrByClusterName(final MQAdminExt adminExt, final String clusterName); static Set<String> fetchMasterAndSlaveAddrByClusterName(final MQAdminExt adminExt, final String clusterName); static Set<String> fetchBrokerNameByClusterName(final MQAdminExt adminExt, final String clusterName); static String fetchBrokerNameByAddr(final MQAdminExt adminExt, final String addr);  }### Answer:
@Test public void testFetchMasterAndSlaveDistinguish() throws InterruptedException, MQBrokerException, RemotingTimeoutException, RemotingSendRequestException, RemotingConnectException { Map<String, List<String>> result = CommandUtil.fetchMasterAndSlaveDistinguish(defaultMQAdminExtImpl, "default-cluster"); assertThat(result.get(null).get(0)).isEqualTo("127.0.0.1:10911"); }