### Question:
DockerUtil { public static DockerUtil getInstance() { if (instance == null) { synchronized (DockerUtil.class) { if (instance == null) instance = new DockerUtil(); } } return instance; } 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 testGetInstanceIsSameAsMock() { assertSame(dockerUtil, DockerUtil.getInstance()); }