Mock Projection Result Spring Data JPA - mockito

Question

I am using spring data jpa in my spring boot project.
I am firing an JPQL query and using an projection to store the result of query.
My Projection :
public interface VeryBasicProjection {
String getTitle();
String getUrl();
}
My service calling this projection :
public List<VeryBasicDTO> getLatestData(int limit){
// Pageable for Limit
Pageable pageable = new PageRequest(0, limit);
// Get Data from DB
List<VeryBasicProjection> latestData = tableRepository.getLatestData("live", 2,pageable);
List<VeryBasicDTO> responseDTO = new ArrayList<>();
// Map Projection to DTO
for(VeryBasicProjection veryBasicProjection : latestData){
VeryBasicDTO veryBasicDTO = new VeryBasicDTO();
veryBasicDTO.buildDTO(veryBasicProjection);
responseDTO.add(veryBasicDTO);
}
return responseDTO;
}
Now I want to test this service using Mockito(Unit Test Case)
I am mocking the call to repository
using when and thenReturn.
My question is how do I mock the result of repository? What should be in thenReturn? I mean how do I create instance of projection and setData to it?

Answer 1

If you want to create an instance of your projection without creating a class implementing the interface, you can use SpelAwareProxyProjectionFactory.
import org.springframework.data.projection.ProjectionFactory;
import org.springframework.data.projection.SpelAwareProxyProjectionFactory;
// ...
ProjectionFactory factory = new SpelAwareProxyProjectionFactory();
VeryBasicProjection projection = factory.createProjection(VeryBasicProjection.class);
projection.setTitle("theTitle");
projection.setUrl("theUrl");
You also need to add setters in your projection:
public interface VeryBasicProjection {
String getTitle();
String getUrl();
void setTitle(String title);
void setUrl(String url);
}
Source: https://github.com/spring-projects/spring-data-examples/blob/master/rest/projections/src/test/java/example/springdata/rest/projections/SimpleProjectionTests.java

Answer 2

This is the simplest way to mock projections in TEST
VeryBasicProjection VeryBasicProjection = new VeryBasicProjection() {
String getTitle() {
return "Title";
}
String getUrl() {
return "url";
}
};

Answer 3

As an addition to Nis' answer:
If the interface doesn't have setters, the projection can be initialized with a map:
ProjectionFactory factory = new SpelAwareProxyProjectionFactory();
Map<String, String> map = Map.of(
"title", "theTitle",
"url", "theUrl"
);
VeryBasicProjection projection = factory.createProjection(VeryBasicProjection.class, map);

Answer 4

We have implemented the same stuff in below way
First mocked the two type of objects:
#Mock
private EntityManager em;
#Mock
private DemoProjectRepo demoProjectRepo;
My demoProjectRepo.findByAll returns List<DemoProjectDevices>
DemoProjectDevices device1 = new DemoProjectDevices();
device1.setAcctNbr("2365897412236589");
device1.setdeviceSeq(new BigDecimal(1));
device1.setCrteTms("2017-07-29 01:21:44.910807");
List<DemoProjectDevices> demoProjectDevices = new ArrayList<DemoProjectDevices>();
demoProjectDevices.add(device1);
For the mock when and thenReturn:
Mockito.when(demoProjectRepo.findByAll("2365897412236589", em))
.thenReturn(demoProjectDevices);

Answer 5

In your projection interface you need to add setters for the values you have getters for.
So when you have a concrete class implementing the projection interface you can add the values to that class so you might have something along these lines:
public interface VeryBasicProjection {
String getTitle();
String getUrl();
void setTitle(String title);
void setUrl(String url);
}
public class VeryBasicProjectionImpl implements VeryBasicProjection{
//add implementing methods
}
////
#Mock
Repository tableRepo;
#InjectMocks
ClassUnderTest c;
#Test
public void test(){
// Pageable for Limit
Pageable pageable = new PageRequest(0, limit);
VeryBasicProjection vbp = new VeryBasicProjectionImpl();
// add data to object here using the setters
List<VeryBasicProjection> projList = new ArrayList<>()
//add objects created
when(tableRepo.getLatestData("live", 2, pageable)).thenReturn(projList));
}