@Test
public void timeoutIsSerializedAsString() {

    final int durationAmountSeconds = 2;
    final Duration timeout = Duration.ofSeconds(durationAmountSeconds);
    final DittoHeaders underTest = DittoHeaders.newBuilder()
            .timeout(timeout)
            .build();
    final JsonObject jsonObject = underTest.toJson();
    assertThat(jsonObject.getValue(DittoHeaderDefinition.TIMEOUT.getKey()))
            .contains(JsonValue.of(durationAmountSeconds * 1000 + "ms"));
}