potat0x/nomock

In-memory implementations of Spring Data JPA repositories (alternative for mocks)

Nomock

Spring Data JPA repositories backed by HashMap (alternative for mocks).

If you dont want to use Testcontainers or H2 database, its worth to considering in-memory repository instead of mocks.

Features

• CrudRepository (fully supported)
• PagingAndSortingRepository (fully supported)
• JpaRepository (queries by Example not implemented)

What are the benefits of using HashMap over repository mocks?

• to write tests, we dont have to investigate how service use repository
• service can be tested as blackbox
  • give input and verify output
  • refactor with ease

Requirements

• entity must have ID field annotated with @Id

Example

Simple Spring Boot app:

@Service
class BookService {

    private final BookRepository bookRepository;

    @Autowired
    BookService(BookRepository bookRepository) {
        this.bookRepository = bookRepository;
    }
}

@Repository
interface BookRepository extends JpaRepository<BookEntity, Long> {
}

@Entity
public final class BookEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String name;

    //...

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        BookEntity that = (BookEntity) o;
        return Objects.equals(id, that.id);
    }

    @Override
    public int hashCode() {
        return Objects.hash(id);
    }
}

How to test BookService using in-memory repository?

1. Create new repository class, that
   • extends one of three available repositories: InMemoryJpaRepository or InMemoryCrudRepository or InMemoryPagingAndSortingRepository. In this case we use InMemoryJpaRepository
   • implements entity`s repository interface

class InMemoryBookRepository extends InMemoryJpaRepository<BookEntity, Long> implements BookRepository {
    public InMemoryBookRepository() {
        super(1L, IdGenerators.IncrementalLongIdGenerator);
    }
}

2. Pass instance of this class to service: BookServiceTest.java

public class BookServiceTest {

    BookService bookService = new BookService(new InMemoryBookRepository());

    @Test
    public test() {
        //...
    }
}

3. Everything is ready to write tests

Check out entire code of this example:

• src/main/.../bookapp
• src/test/.../bookapp