public Optional<Object> retrieveSingleValue(final Object jsonObject, final String valueName) {
        final Map<String, Object> map = objectMapper.convertValue(jsonObject, new TypeReference<>() {});
        return Optional.ofNullable(map.get(valueName));
    }
@Test
    void testRetrievesEmptyOptionalOnWrongValueName() {
        Optional<Object> value = toTest.retrieveSingleValue(new TestJson(42, "ho!"), "carramba!");
        assertTrue(value.isEmpty());
    }