@Test
public void mapFromNonMessageCommand() {

    final Signal<?> signal = ThingDeleted.of(ThingId.of("thing:id"), 25L, DittoHeaders.empty());
    final Adaptable adaptable = ADAPTER.toAdaptable(signal);
    final List<ExternalMessage> actualExternalMessages = underTest.map(adaptable);
    final List<ExternalMessage> expectedExternalMessages = new DittoMessageMapper().map(adaptable);
    assertThat(actualExternalMessages).isEqualTo(expectedExternalMessages);
}