@Test
    public void testRemoveMembersFromGroup() throws Exception {
        try (AdminClientUnitTestEnv env = mockClientEnv()) {
            final String instanceOne = "instance-1";
            final String instanceTwo = "instance-2";

            env.kafkaClient().setNodeApiVersions(NodeApiVersions.create());

            // Retriable FindCoordinatorResponse errors should be retried
            env.kafkaClient().prepareResponse(prepareFindCoordinatorResponse(Errors.COORDINATOR_LOAD_IN_PROGRESS, Node.noNode()));
            env.kafkaClient().prepareResponse(prepareFindCoordinatorResponse(Errors.NONE, env.cluster().controller()));

            // Retriable errors should be retried
            env.kafkaClient().prepareResponse(new LeaveGroupResponse(new LeaveGroupResponseData()
                                                                         .setErrorCode(Errors.COORDINATOR_LOAD_IN_PROGRESS.code())));

            // Inject a top-level non-retriable error
            env.kafkaClient().prepareResponse(new LeaveGroupResponse(new LeaveGroupResponseData()
                                                                         .setErrorCode(Errors.UNKNOWN_SERVER_ERROR.code())));

            Collection<MemberToRemove> membersToRemove = asList(new MemberToRemove(instanceOne),
                                                                       new MemberToRemove(instanceTwo));
            final RemoveMembersFromConsumerGroupResult unknownErrorResult = env.adminClient().removeMembersFromConsumerGroup(
                GROUP_ID,
                new RemoveMembersFromConsumerGroupOptions(membersToRemove)
            );

            MemberToRemove memberOne = new MemberToRemove(instanceOne);
            MemberToRemove memberTwo = new MemberToRemove(instanceTwo);

            TestUtils.assertFutureError(unknownErrorResult.memberResult(memberOne), UnknownServerException.class);
            TestUtils.assertFutureError(unknownErrorResult.memberResult(memberTwo), UnknownServerException.class);

            MemberResponse responseOne = new MemberResponse()
                                             .setGroupInstanceId(instanceOne)
                                             .setErrorCode(Errors.UNKNOWN_MEMBER_ID.code());

            MemberResponse responseTwo = new MemberResponse()
                                             .setGroupInstanceId(instanceTwo)
                                             .setErrorCode(Errors.NONE.code());

            // Inject one member level error.
            env.kafkaClient().prepareResponse(prepareFindCoordinatorResponse(Errors.NONE, env.cluster().controller()));
            env.kafkaClient().prepareResponse(new LeaveGroupResponse(new LeaveGroupResponseData()
                                                                         .setErrorCode(Errors.NONE.code())
                                                                         .setMembers(asList(responseOne, responseTwo))));

            final RemoveMembersFromConsumerGroupResult memberLevelErrorResult = env.adminClient().removeMembersFromConsumerGroup(
                GROUP_ID,
                new RemoveMembersFromConsumerGroupOptions(membersToRemove)
            );

            TestUtils.assertFutureError(memberLevelErrorResult.all(), UnknownMemberIdException.class);
            TestUtils.assertFutureError(memberLevelErrorResult.memberResult(memberOne), UnknownMemberIdException.class);
            assertNull(memberLevelErrorResult.memberResult(memberTwo).get());

            // Return with missing member.
            env.kafkaClient().prepareResponse(prepareFindCoordinatorResponse(Errors.NONE, env.cluster().controller()));
            env.kafkaClient().prepareResponse(new LeaveGroupResponse(new LeaveGroupResponseData()
                                                                         .setErrorCode(Errors.NONE.code())
                                                                         .setMembers(Collections.singletonList(responseTwo))));

            final RemoveMembersFromConsumerGroupResult missingMemberResult = env.adminClient().removeMembersFromConsumerGroup(
                GROUP_ID,
                new RemoveMembersFromConsumerGroupOptions(membersToRemove)
            );

            TestUtils.assertFutureError(missingMemberResult.all(), IllegalArgumentException.class);
            // The memberOne was not included in the response.
            TestUtils.assertFutureError(missingMemberResult.memberResult(memberOne), IllegalArgumentException.class);
            assertNull(missingMemberResult.memberResult(memberTwo).get());


            // Return with success.
            env.kafkaClient().prepareResponse(prepareFindCoordinatorResponse(Errors.NONE, env.cluster().controller()));
            env.kafkaClient().prepareResponse(new LeaveGroupResponse(
                    new LeaveGroupResponseData().setErrorCode(Errors.NONE.code()).setMembers(
                        asList(responseTwo,
                                      new MemberResponse().setGroupInstanceId(instanceOne).setErrorCode(Errors.NONE.code())
                        ))
            ));

            final RemoveMembersFromConsumerGroupResult noErrorResult = env.adminClient().removeMembersFromConsumerGroup(
                GROUP_ID,
                new RemoveMembersFromConsumerGroupOptions(membersToRemove)
            );
            assertNull(noErrorResult.all().get());
            assertNull(noErrorResult.memberResult(memberOne).get());
            assertNull(noErrorResult.memberResult(memberTwo).get());

            // Test the "removeAll" scenario
            final List<TopicPartition> topicPartitions = Stream.of(1, 2, 3).map(partition -> new TopicPartition("my_topic", partition))
                    .collect(Collectors.toList());
            // construct the DescribeGroupsResponse
            DescribeGroupsResponseData data = prepareDescribeGroupsResponseData(GROUP_ID, asList(instanceOne, instanceTwo), topicPartitions);

            // Return with partial failure for "removeAll" scenario
            // 1 prepare response for AdminClient.describeConsumerGroups
            env.kafkaClient().prepareResponse(prepareFindCoordinatorResponse(Errors.NONE, env.cluster().controller()));
            env.kafkaClient().prepareResponse(new DescribeGroupsResponse(data));

            // 2 KafkaAdminClient encounter partial failure when trying to delete all members
            env.kafkaClient().prepareResponse(prepareFindCoordinatorResponse(Errors.NONE, env.cluster().controller()));
            env.kafkaClient().prepareResponse(new LeaveGroupResponse(
                    new LeaveGroupResponseData().setErrorCode(Errors.NONE.code()).setMembers(
                            asList(responseOne, responseTwo))
            ));
            final RemoveMembersFromConsumerGroupResult partialFailureResults = env.adminClient().removeMembersFromConsumerGroup(
                    GROUP_ID,
                    new RemoveMembersFromConsumerGroupOptions()
            );
            ExecutionException exception = assertThrows(ExecutionException.class, () -> partialFailureResults.all().get());
            assertInstanceOf(KafkaException.class, exception.getCause());
            assertInstanceOf(UnknownMemberIdException.class, exception.getCause().getCause());

            // Return with success for "removeAll" scenario
            // 1 prepare response for AdminClient.describeConsumerGroups
            env.kafkaClient().prepareResponse(prepareFindCoordinatorResponse(Errors.NONE, env.cluster().controller()));
            env.kafkaClient().prepareResponse(new DescribeGroupsResponse(data));

            // 2. KafkaAdminClient should delete all members correctly
            env.kafkaClient().prepareResponse(prepareFindCoordinatorResponse(Errors.NONE, env.cluster().controller()));
            env.kafkaClient().prepareResponse(new LeaveGroupResponse(
                    new LeaveGroupResponseData().setErrorCode(Errors.NONE.code()).setMembers(
                            asList(responseTwo,
                                    new MemberResponse().setGroupInstanceId(instanceOne).setErrorCode(Errors.NONE.code())
                            ))
            ));
            final RemoveMembersFromConsumerGroupResult successResult = env.adminClient().removeMembersFromConsumerGroup(
                    GROUP_ID,
                    new RemoveMembersFromConsumerGroupOptions()
            );
            assertNull(successResult.all().get());
        }
    }
Test that we propagate exceptions encountered when fetching metadata.
clients/src/test/java/org/apache/kafka/clients/admin/KafkaAdminClientTest.java