### Question:
DockerUtil { public String getDockerBridgeName() { LoggingService.logDebug(MODULE_NAME , "get docker bridge name"); List<Network> networks = dockerClient.listNetworksCmd().exec(); Network dockerBridge = networks .stream() .filter(network -> network.getOptions().getOrDefault("com.docker.network.bridge.default_bridge", "false").equals("true")) .findFirst() .orElse(null); if (dockerBridge == null) { return null; } LoggingService.logDebug(MODULE_NAME , "Finished get docker bridge name"); return dockerBridge.getOptions().get("com.docker.network.bridge.name"); } private  DockerUtil(); static DockerUtil getInstance(); void reInitDockerClient(); String getDockerBridgeName(); void startContainer(Microservice microservice); void stopContainer(String id); void removeContainer(String id, Boolean withRemoveVolumes); @SuppressWarnings("deprecation") String getContainerIpAddress(String id); String getContainerName(Container container); String getContainerMicroserviceUuid(Container container); static String getIoFogContainerName(String microserviceUuid); Optional<Container> getContainer(String microserviceUuid); MicroserviceStatus getMicroserviceStatus(String containerId); List<Container> getRunningContainers(); List<Container> getRunningIofogContainers(); Optional<Statistics> getContainerStats(String containerId); long getContainerStartedAt(String id); boolean areMicroserviceAndContainerEqual(String containerId, Microservice microservice); Optional<String> getContainerStatus(String containerId); boolean isContainerRunning(String containerId); List<Container> getContainers(); void removeImageById(String imageId); @SuppressWarnings("resource") void pullImage(String imageName, String microserviceUuid, Registry registry); boolean findLocalImage(String imageName); String createContainer(Microservice microservice, String host); PruneResponse dockerPrune(); void update(PullResponseItem item, Map<String, ItemStatus> statuses);  }### Answer:
@Test public void tesGetDockerBridgeNameWhenNewtorkIsEmpty() { assertNull(dockerUtil.getDockerBridgeName()); }