@Test
public void getManifestFromThingCommand() {

    final ThingId thingId = THING_ID;
    final Command<RetrieveThing> retrieveThing = RetrieveThing.of(thingId, DittoHeaders.empty());
    final String manifest = underTest.apply(retrieveThing);
    assertThat(manifest).isEqualTo(retrieveThing.getType());
}