[FIXED] How to deal with Page while unit testing with mockito and Junit

Issue

I want to mock database call with fake data but I got stuck in the following scenario:

MyService

public class MyService {
    // some stuff

    Page<SampleDto> sample = repo.findAllSample();

    // other stuff
}

I want to stub this with when() but I am not able to do this. My test is: MyServiceTest

public class MySampleTest {

    @Test
    void myTest() {
        // initialisation and all stuff

        when(myRepo.findAll()).thenReturn(......)
        // I want to pass 2 fake SampleDto from 
        // here but don't know how to do that
    }
}

Solution

You can mock the Page object also if there is a aneed to handle some other functionality inside your service class. Assuming that your service class is actually something like:

public class MyService {
    @Resource
    private SampleRepository repo;

    public Page<SampleDto> findAllSample() {
        var sampleData = repo.findAllSample();
        // perhaps some operations with sample data and page
        return sampleData;
    }
}

then the test class could be something like (JUnit4):

@RunWith(MockitoJUnitRunner.class)
public class MySampleTest {
    @Mock
    private SampleRepository repo;
    @Mock
    private Page<SampleDto> page;
    @InjectMocks
    private MyService myService;

    @Test
    public void test() {
    doReturn(page).when(repo).findAll();
    var listSampleDtos = List.of(new SampleDto()); // populate with what you need
    doReturn(listSampleDtos).when(page).getContent();
    var page = myService.findAllSample();
    // ... do the asserts, just as an example:
    verify(repo).findAll(); // called
    assertEquals(1, page.getContent().size());
    }

Answered By - pirho