@Test
public void testGetContainerEnvForDocker() {

  Configuration conf = mock(Configuration.class);
  when(conf.getBoolean(TonyConfigurationKeys.DOCKER_ENABLED,
          TonyConfigurationKeys.DEFAULT_DOCKER_ENABLED))
          .thenReturn(true);
  assertEquals(Utils.getContainerEnvForDocker(conf, "tony.worker.gpus"),
          new HashMap<>());
  when(conf.get(TonyConfigurationKeys
          .getDockerImageKey("tony.worker.gpus"))).thenReturn("foo");
  assertEquals(Utils.getContainerEnvForDocker(conf, "tony.worker.gpus"),
          new HashMap<>());
}