@Test
public void toJsonReturnsExpected() {

    final RetrieveThingsResponse underTest = RetrieveThingsResponse
            .of(Collections.singletonList(TestConstants.Thing.THING), FieldType.notHidden(), "example.com",
                    TestConstants.EMPTY_DITTO_HEADERS);
    final JsonObject actualJson = underTest.toJson();
    assertThat(actualJson).isEqualTo(KNOWN_JSON);
}