@Test
    public void testUnregisterBroker() throws Throwable {
        try (
            LocalLogManagerTestEnv logEnv = new LocalLogManagerTestEnv.Builder(1).
                build();
            QuorumControllerTestEnv controlEnv = new QuorumControllerTestEnv.Builder(logEnv).
                setControllerBuilderInitializer(controllerBuilder ->
                    controllerBuilder.setConfigSchema(SCHEMA)
                ).
                build()
        ) {
            ListenerCollection listeners = new ListenerCollection();
            listeners.add(new Listener().setName("PLAINTEXT").
                setHost("localhost").setPort(9092));
            QuorumController active = controlEnv.activeController();
            CompletableFuture<BrokerRegistrationReply> reply = active.registerBroker(
                ANONYMOUS_CONTEXT,
                new BrokerRegistrationRequestData().
                    setBrokerId(0).
                    setClusterId(active.clusterId()).
                    setIncarnationId(Uuid.fromString("kxAT73dKQsitIedpiPtwBA")).
                    setFeatures(brokerFeatures(MetadataVersion.IBP_3_0_IV1, MetadataVersion.latestTesting())).
                    setLogDirs(Collections.singletonList(Uuid.fromString("vBpaRsZVSaGsQT53wtYGtg"))).
                    setListeners(listeners));
            assertEquals(5L, reply.get().epoch());
            CreateTopicsRequestData createTopicsRequestData =
                new CreateTopicsRequestData().setTopics(
                    new CreatableTopicCollection(Collections.singleton(
                        new CreatableTopic().setName("foo").setNumPartitions(1).
                            setReplicationFactor((short) 1)).iterator()));
            assertEquals(Errors.INVALID_REPLICATION_FACTOR.code(), active.createTopics(
                ANONYMOUS_CONTEXT,
                createTopicsRequestData, Collections.singleton("foo")).get().
                    topics().find("foo").errorCode());
            assertEquals("Unable to replicate the partition 1 time(s): All brokers " +
                "are currently fenced.", active.createTopics(ANONYMOUS_CONTEXT,
                    createTopicsRequestData, Collections.singleton("foo")).
                        get().topics().find("foo").errorMessage());
            assertEquals(new BrokerHeartbeatReply(true, false, false, false),
                active.processBrokerHeartbeat(ANONYMOUS_CONTEXT, new BrokerHeartbeatRequestData().
                        setWantFence(false).setBrokerEpoch(5L).setBrokerId(0).
                        setCurrentMetadataOffset(100000L)).get());
            assertEquals(Errors.NONE.code(), active.createTopics(ANONYMOUS_CONTEXT,
                createTopicsRequestData, Collections.singleton("foo")).
                    get().topics().find("foo").errorCode());
            CompletableFuture<TopicIdPartition> topicPartitionFuture = active.appendReadEvent(
                "debugGetPartition", OptionalLong.empty(), () -> {
                    Iterator<TopicIdPartition> iterator = active.
                        replicationControl().brokersToIsrs().iterator(0, true);
                    assertTrue(iterator.hasNext());
                    return iterator.next();
                });
            assertEquals(0, topicPartitionFuture.get().partitionId());
            active.unregisterBroker(ANONYMOUS_CONTEXT, 0).get();
            topicPartitionFuture = active.appendReadEvent(
                "debugGetPartition", OptionalLong.empty(), () -> {
                    Iterator<TopicIdPartition> iterator = active.
                        replicationControl().brokersToIsrs().partitionsWithNoLeader();
                    assertTrue(iterator.hasNext());
                    return iterator.next();
                });
            assertEquals(0, topicPartitionFuture.get().partitionId());

            testToImages(logEnv.allRecords());
        }
    }
Test that an incrementalAlterConfigs operation doesn't complete until the records
can be written to the metadata log.
metadata/src/test/java/org/apache/kafka/controller/QuorumControllerTest.java