How to call real methods of jpa repository in Junit5 mockito test cases for springboot services

Question

I have below repository interface which is getting used in my service class.

@Repository
public interface InventoryRepository extends JpaRepository<Inventory, Integer> {    
        Inventory findByInventoryIdAndCompanyId(Integer inventoryId, Integer companyId);   
    }

In My service test class, I have these two dependencies

 @InjectMocks
 InventoryService inventoryService;
        
 @Mock
 InventoryRepository inventoryRepository;

Also, Below is my test method in the same class

 @Test
 public void getInventoryByIdTest() {
        when(inventoryRepository.findByInventoryIdAndCompanyId(16591,1)).thenCallRealMethod();
        Assertions.assertEquals(16591,inventoryService.getInventoryById(16591 , 1).getInventoryId());
    }

I am trying to write a test case for a service and this service internally calls the JPA repository method to get the data from DB. I want to invoke the real method of the JPA repository and I want to get the real db result instead of mocking it. But it is not working and throwing the below error.

org.mockito.exceptions.base.MockitoException: 
Cannot call abstract real method on java object!
Calling real methods is only possible when mocking non abstract method.

//correct example:
when(mockOfConcreteClass.nonAbstractMethod()).thenCallRealMethod();

Is there any possible way to work it out?

Answer 1

Let's try to replace the interface InventoryService with its implementation in your junit and use @Spy instead of @Mock .

Hint

Your test is an integration test, not an unit test. You are testing that your application comunicates without any problems with your database; unfortunately this type of test requires many resources and too much time (let's immagine having handreds of test and each of this open a connection to the database). The unit tests are useful in order to verify the buisness logic of your application and, since they don't require a lot of resources and if they do we can use mock interfaces or services or whatever, they should take less then one second per test.

I suggest you to read this of article of Martin Flower