### Question:
PsuDataMapper { public List<PsuIdData> mapToPsuIdDataList(List<PsuData> psuIdDataList) { return psuIdDataList.stream() .map(this::mapToPsuIdData) .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 mapToPsuIdDataList() { PsuData psuData = jsonReader.getObjectFromFile("json/service/mapper/psu-data.json", PsuData.class); PsuIdData expected = jsonReader.getObjectFromFile("json/service/mapper/psu-id-data.json", PsuIdData.class); List<PsuIdData> expectedList = Collections.singletonList(expected); List<PsuIdData> psuDataList = psuDataMapper.mapToPsuIdDataList(Collections.singletonList(psuData)); verify(psuDataMapper, times(1)).mapToPsuIdData(psuData); assertEquals(expectedList, psuDataList); }