I am writing unit tests for service class. Let’s call it MyService, which is in the following format:

public class MyService {

    private final HttpHeaders headers = new HttpHeaders();

    public MyService(MyRepository myRepository) {
        headers.setBasicAuth(myRepository.getValue("login"), myRepository.getValue("password"));
  }
   
   // OTHER PARTS OF THE CODE
}

In the constructor of MyService class, I am setting values to headers field. When writing unit tests, I am facing the problem which will be described below:

@ContextConfiguration(classes = MyService.class)
class MyServiceTest {

    @Autowired
    private MyService myService;

    @BeforeEach
    void init() {
        mockValue("login", "login_value");
        mockValue("password", "password_value");
    }

   // OTHER PARTS OF THE CODE
}

I have a method mockValue which mocks the values appropriately. the problem is:

THE CONSTRUCTOR OF MyService WORKS BEFORE THE init() METHOD OF MyServiceTest. AS A RESULT, myRepository.getValue("login") IS RETURNING NULL, AND headers.setBasicAuth() METHOD IS THROWING EXCEPTION : “Username must not be null”.

HOW TO HANDLE IT? HOW TO MOCK VALUES BEFORE THE CONSTUCTOR OF MyService WORKS.

I TRIED TO CREATE ANOTHER CLASS, INSIDE WHICH I CAN MOCK VALUES. AND INJECT IT TO MY TEST CLASS.

IT DIDN’T WORK AS I EXCEPTED.