public void updateGroupConfig(String groupId, Properties newGroupConfig) {
        if (null == groupId || groupId.isEmpty()) {
            throw new InvalidRequestException("Group name can't be empty.");
        }

        final GroupConfig newConfig = GroupConfig.fromProps(
            defaultConfig.originals(),
            newGroupConfig
        );
        configMap.put(groupId, newConfig);
    }
@Test
    public void testUpdateGroupConfig() {
        String groupId = "foo";
        Properties props = new Properties();
        props.put(CONSUMER_SESSION_TIMEOUT_MS_CONFIG, 50000);
        props.put(CONSUMER_HEARTBEAT_INTERVAL_MS_CONFIG, 6000);
        configManager.updateGroupConfig(groupId, props);

        Optional<GroupConfig> configOptional = configManager.groupConfig(groupId);
        assertTrue(configOptional.isPresent());

        GroupConfig config = configOptional.get();
        assertEquals(50000, config.getInt(CONSUMER_SESSION_TIMEOUT_MS_CONFIG));
        assertEquals(6000, config.getInt(CONSUMER_HEARTBEAT_INTERVAL_MS_CONFIG));
    }