how to test MapStruct mapper implementation and mock its dependencies

Question

I am using MapStruct to map objects from and to DTOs. My mappers are dependent on some services/repositories to get data from database when for example mapping from DTo that has list of IDs to POJO that has a list of other POJOs. For this I have a Mapper inteface and an abstract class Decorator implementing this interface. I want to test the mapper but I need to mock the services inside the decorator. My question is how can I achieve this?

Now I know there would be better if mapper didn't have so much dependencies (SOLID), but I need to finish the project fast now.

It looks like this:

Mapper

@Mapper(componentModel = "spring", injectionStrategy = InjectionStrategy.CONSTRUCTOR)
@DecoratedWith(AuthorMapperDecorator.class)
public interface AuthorMapper {

    AuthorDTO map(Author entity);

    @Mapping(target = "songs", ignore = true)
    Author map(AuthorDTO dto);

    @Mapping(target = "coauthorSongs", ignore = true)
    @Mapping(target = "songs", ignore = true)
    @Mapping(target = "id", ignore = true)
    @Mapping(target = "name", source = "name")
    Author map(UniversalCreateDTO dto);
}

Decorator

public abstract class AuthorMapperDecorator implements AuthorMapper {

  @Autowired
  @Qualifier("delegate")
  private AuthorMapper delegate;
  @Autowired
  private SongCoauthorService songCoauthorService;
  @Autowired
  private SongService songService;

  @Override
  public Author map(AuthorDTO dto) {
    var author = delegate.map(dto);
    author.setBiographyUrl(null);
    author.setPhotoResource(null);
    author.setCoauthorSongs(new HashSet<>(songCoauthorService.findByAuthorId(dto.getId())));
    author.setSongs(new HashSet<>(songService.findByAuthorId(dto.getId())));
    return author;
  }

  @Override
  public Author map(UniversalCreateDTO dto) {
    var author = delegate.map(dto);
    author.setSongs(new HashSet<>());
    author.setCoauthorSongs(new HashSet<>());
    author.setId(Constants.DEFAULT_ID);
    return author;
  }
}

Then there are the generated implementations:

@Generated(
    value = "org.mapstruct.ap.MappingProcessor",
    date = "2020-05-13T22:50:36+0200",
    comments = "version: 1.3.1.Final, compiler: javac, environment: Java 13.0.2 (Oracle Corporation)"
)
@Component
@Qualifier("delegate")
public class AuthorMapperImpl_ implements AuthorMapper {

    @Override
    public AuthorDTO map(Author entity) {
        if ( entity == null ) {
            return null;
        }

        Builder authorDTO = AuthorDTO.builder();

        authorDTO.id( entity.getId() );
        authorDTO.name( entity.getName() );

        return authorDTO.build();
    }

    @Override
    public Author map(AuthorDTO dto) {
        if ( dto == null ) {
            return null;
        }

        Author author = new Author();

        author.setId( dto.getId() );
        author.setName( dto.getName() );

        return author;
    }

    @Override
    public Author map(UniversalCreateDTO dto) {
        if ( dto == null ) {
            return null;
        }

        Author author = new Author();

        author.setName( dto.getName() );

        return author;
    }
}

@Generated(
    value = "org.mapstruct.ap.MappingProcessor",
    date = "2020-05-13T22:50:36+0200",
    comments = "version: 1.3.1.Final, compiler: javac, environment: Java 13.0.2 (Oracle Corporation)"
)
@Component
@Primary
public class AuthorMapperImpl extends AuthorMapperDecorator implements AuthorMapper {

    private final AuthorMapper delegate;

    @Autowired
    public AuthorMapperImpl(@Qualifier("delegate") AuthorMapper delegate) {

        this.delegate = delegate;
    }

    @Override
    public AuthorDTO map(Author entity)  {
        return delegate.map( entity );
    }
}

Answer 1

Okay, I found an answer minutes after asking thr question. So ironic.

I am going to post it here if somebody needs it.

You just need to add Setters to the decorator for the services/repositories and test the implementation that has the mocks set in place of the dependencies.

Like this:

Decorator:

@Setter
public abstract class AuthorMapperDecorator implements AuthorMapper {

  @Autowired
  @Qualifier("delegate")
  private AuthorMapper delegate;
  @Autowired
  private SongCoauthorService songCoauthorService;
  @Autowired
  private SongService songService;

  @Override
  public Author map(AuthorDTO dto) {
    var author = delegate.map(dto);
    author.setBiographyUrl(null);
    author.setPhotoResource(null);
    author.setCoauthorSongs(new HashSet<>(songCoauthorService.findByAuthorId(dto.getId())));
    author.setSongs(new HashSet<>(songService.findByAuthorId(dto.getId())));
    return author;
  }

  @Override
  public Author map(UniversalCreateDTO dto) {
    var author = delegate.map(dto);
    author.setSongs(new HashSet<>());
    author.setCoauthorSongs(new HashSet<>());
    author.setId(Constants.DEFAULT_ID);
    return author;
  }
}

Test:

@ExtendWith(MockitoExtension.class)
@SpringBootTest(classes = { StkSongbookApplication.class, AuthorMapperImpl.class })
class AuthorMapperTest {

  @Mock
  private SongService songService;

  @Mock
  private SongCoauthorService songCoauthorService;

  @Autowired
  private AuthorMapperImpl impl;

  private AuthorMapper mapper;

  @BeforeEach
  void setUp() {
    impl.setSongCoauthorService(songCoauthorService);
    impl.setSongService(songService);
    mapper = impl;
  }

  @Test
  void testMapToDTO() {
    Author author = new Author();
    author.setId(1L);
    author.setName("dummy name");
    author.setSongs(new HashSet<>());
    author.setCoauthorSongs(new HashSet<>());

    AuthorDTO dto = mapper.map(author);

    assertEquals(author.getName(), dto.getName());
    assertEquals(author.getId(), dto.getId());
  }

  @Test
  void testMapToEntity() {
    AuthorDTO author = AuthorDTO.builder().id(1L).name("dummy name").build();

    Song song1 = new Song();
    song1.setId(1L);
    song1.setTitle("title song1");

    given(songService.findByAuthorId(1L)).willReturn(List.of(new Song[]{song1}));

    Author mapped = mapper.map(author);

    assertEquals(author.getId(), mapped.getId());
    assertEquals(author.getName(), mapped.getName());
    assertEquals(1, mapped.getSongs().size());
  }
}