Unit testing a method which calls a method returning a page of an entitiy

Question

I would like to test the following method, for the case when I know the underlying call to findAllByMerchantId() method returns a fixed number of results (a page with fixed number of entities).

public ListBeneficiaryResponseDTO getBeneficiariesOfMerchant(Long merchantId, Integer page, Integer pageSize,
                                                             String sortDirection, String sortField) {

    // default we are setting to added on desc sort
    Sort sort = Sort.by(Sort.Direction.DESC,"addedOn");
    if(sortField != null && sortDirection != null) {
        sort = Sort.by(Sort.Direction.fromString(sortDirection),sortField);
    }

    Pageable pageRequest = PageRequest.of(page-1, pageSize, sort);
    Page<Beneficiary> pageOfBeneficiaries = beneficiaryRepository.findAllByMerchantId(merchantId, pageRequest);

    List<BeneficiaryResponseDTO> benResonseDtoList = new ArrayList<BeneficiaryResponseDTO>();

    for( Beneficiary ben: pageOfBeneficiaries.getContent()) {
        benResonseDtoList.add(this.getBeneficiaryResponseDTO(ben));
    }
    ListBeneficiaryResponseDTO formattedListBen = new ListBeneficiaryResponseDTO(pageOfBeneficiaries.getTotalPages(),pageOfBeneficiaries.getTotalElements(),pageOfBeneficiaries.getNumber(),benResonseDtoList);
    return formattedListBen;
}

How do I mock the response of findAllByMerchantId() call, to return a fixed number of results in a page?

PS Beginner at unit testing..

Answer 1

You can use mockito together with junit . Mockito is the framework we are going to use for mocking objects and stubing methods. Junit for running the test.

public class Test {

   @Mock
   private BeneficiaryRepository beneficiaryRepository;

   @Test
    public void testGetBeneficiariesOfMerchant()  {
//your code ...
        Page<Beneficiary> pages = // your initialization  
when(beneficiaryRepository.findAllByMerchantId(any(),any())).thenReturn(pages);
//your code ...
    }

}

Check the link below for more info: https://www.vogella.com/tutorials/Mockito/article.html

Answer 2

@Mock public Page findAllByMerchantId(merchantId, pageRequest) throws IOException{ //create object of desired class and return. return obj; }

You can try with above approach.