### Question:
PsuDataMapper { public List<PsuData> mapToPsuDataList(List<PsuIdData> psuIdDataList, String instanceId) { return psuIdDataList.stream() .map(psu -> mapToPsuData(psu, instanceId)) .filter(Objects::nonNull) .collect(Collectors.toList()); }  List<PsuData> mapToPsuDataList(List<PsuIdData> psuIdDataList, String instanceId); List<PsuIdData> mapToPsuIdDataList(List<PsuData> psuIdDataList); PsuData mapToPsuData(PsuIdData psuIdData, String instanceId); PsuIdData mapToPsuIdData(PsuData psuData);  }### Answer:
@Test void mapToPsuDataList() { PsuIdData psuIdData = jsonReader.getObjectFromFile("json/service/mapper/psu-id-data.json", PsuIdData.class); PsuData expected = jsonReader.getObjectFromFile("json/service/mapper/psu-data.json", PsuData.class); List<PsuData> expectedList = Collections.singletonList(expected); List<PsuData> psuDataList = psuDataMapper.mapToPsuDataList(Collections.singletonList(psuIdData), DEFAULT_SERVICE_INSTANCE_ID); verify(psuDataMapper, times(1)).mapToPsuData(psuIdData, DEFAULT_SERVICE_INSTANCE_ID); assertEquals(expectedList, psuDataList); }