junit如何覆盖进入.CollectionUtils?isEmpty(disReadings)的if条件？

Question

I am learning junit and trying to junit test the class and I am not able to enter the if.CollectionUtils.isEmpty(disReadings) part of code through the code:

List<DisLRead> disLReadList = new ArrayList<>();
cHlDisList.forEach(dis -> {
List<Double> disReadingsL = disRepository
        .getReadsForDisId(dis.getDisId(), sDate, eDate);
        
if (!CollectionUtils.isEmpty(disReadingsL)) {
    double max = Round.RoundToTwoDecimal(
            disReadingsL.stream().mapToDouble(Double::doubleValue).max().getAsDouble());
    double min = Round.RoundToTwoDecimal(
            disReadingsL.stream().mapToDouble(Double::doubleValue).min().getAsDouble());
    double avg = Round.RoundToTwoDecimal(
            disReadingsL.stream().mapToDouble(Double::doubleValue).average().getAsDouble());
    DisLReading disLReading = new DisLReading();
    disLReading.setDisId(dis.getDisId());
    disLReading.setDisName(dis.getDisName());
    disLReading.setDisZ(dis.getDisZ());
    disLReading.setMax(max);
    disLReading.setMin(min);
    disLReading.setAverage(avg);
    disLReadList.add(disLReading);
}});

Update:

Snippet of my test class:

@Mock
DisRepository disRepository;

@Mock
Round round;
    List<DisLRead> disLReadList = new ArrayList<>();
    List<Double> disReadingsL = new ArrayList<>();
    disReadingsL.add(100.0000);
    disReadingsL.add(200.0000);
    when(disRepository.getReadsForDisId(anyInt(), anyString(), anyString()))
            .thenReturn(disReadingsL);
    assertNotNull(disReadingsL);
    assertEquals(!CollectionUtils.isEmpty(disReadingsL), true);
    

What am I doing wrong? how to enter the cover this part of code. Thanks in advance!

Answer 1

You have more or less two options either use a mocking framework like mockito to create a mock object for "disRepository" it would look like this:

DisrepositoryClass disrepositoryMock = Mockito.mock(disrepository.class);
when(disrepositoryMock.getReadsForDisId(any(),any(),any()).thenReturn(List.of(Double.of(1d)));

Alternativly you create your own Mock object and provide it.

Answer 2

CollectionUtils.isEmpty() is a static method; therefore, you have to use PowerMockito.

mockStatic(CollectionUtils.class);
given(CollectionUtils.isEmpty(anyList())).willReturn(true);