@Test
public void getDaemonOs() {

    DockerClientFacade facade = createFacade(dockerClient);
    dockerClient.setDaemonOs(DockerDaemonOS.WINDOWS.getAttribute());
    Optional<DockerDaemonOS> daemonOS = facade.getDaemonOS();
    assertThat(daemonOS).isEqualTo(Optional.of(DockerDaemonOS.WINDOWS));
    dockerClient.setDaemonOs("not_an_real_os");
    daemonOS = facade.getDaemonOS();
    assertThat(daemonOS).isEmpty();
}