### Question:
DockerUtil { public void removeImageById(String imageId) throws NotFoundException, NotModifiedException { LoggingService.logDebug(MODULE_NAME ,"removing image by id"); dockerClient.removeImageCmd(imageId).withForce(true).exec(); LoggingService.logDebug(MODULE_NAME, String.format("image \"%s\" removed", imageId)); } 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 testRemoveImageById() { dockerUtil.removeImageById(imageID); Mockito.verify(dockerClient).removeImageCmd(anyString()); }
@Test (expected = NotFoundException.class) public void throwsNotFoundExceptionWhenRemoveImageById() { PowerMockito.doThrow(spy(new NotFoundException("Exception"))).when(removeImageCmd).exec(); dockerUtil.removeImageById(imageID); }