@Test
public void addsLiveResponseAckLabelToAlreadyRequiredAckLabels() {

    final AcknowledgementRequest ackRequest1 = AcknowledgementRequest.of(AcknowledgementLabel.of("FOO"));
    final AcknowledgementRequest ackRequest2 = AcknowledgementRequest.of(AcknowledgementLabel.of("BAR"));
    final DittoHeaders dittoHeaders = DittoHeaders.newBuilder()
            .channel("live")
            .acknowledgementRequest(ackRequest1, ackRequest2)
            .randomCorrelationId()
            .responseRequired(true)
            .build();
    final MessageCommand<?, ?> command = SendThingMessage.of(THING_ID, MESSAGE, dittoHeaders);
    final MessageCommandAckRequestSetter underTest = MessageCommandAckRequestSetter.getInstance();
    final DittoHeaders expectedHeaders = dittoHeaders.toBuilder()
            .acknowledgementRequest(ackRequest1, ackRequest2,
                    AcknowledgementRequest.of(DittoAcknowledgementLabel.LIVE_RESPONSE))
            .build();
    final MessageCommand<?, ?> expectedCommand = command.setDittoHeaders(expectedHeaders);
    final MessageCommand<?, ?> appliedCommand = underTest.apply(command);
    assertThat(appliedCommand.getDittoHeaders()).isEqualTo(expectedHeaders);
    assertThat(appliedCommand).isEqualTo(expectedCommand);
}