How to test custom exception with Mockito-CodePudding

I am trying to learn unit testing with Mockito. This is a method I wrote to authenticate the users that tries to log in:

public class AuthenService {
    
    private UserRepo userRepo;  

    public User authenticate(String username, String password) throws UserNotFoundException {
        User user = null;
        if (userRepo.validate(username, password)) {
            user = userRepo.findUsername(username);
            return user;
        } else {
            throw new UserNotFoundException("User not found!");
        }
    }
}

userRepo is an interface with these two abstract methods:

public interface UserRepo{
    
    boolean validate(String username, String password);
    
    User findUsername(String username);
    
}

This is my testing code:

public class Test {

    AuthenService as;
    UserRepo ur;
    
    @BeforeEach
    public void init() {
        ur = mock(UserRepo.class);
        as = new AuthenService(ur);
    }
    
    @Test
    public void authenticate() throws UserNotFoundException {
        when(as.authenticate("abc", "123")).thenThrow(new UserNotFoundException("User not found!"));
    }
}

I suppose as.authenticate("abc", "123") should throw an exception because the DB is empty right now. But I think I am wrong, and I have no idea how to fix it. Can anyone please explain to me? Thank you.

CodePudding user response：

One unit test would be to expect an exception if the validation fails. To that, consider (working example here:

   @Test(expected = UserNotFoundException.class)
    public void authenticate() throws UserNotFoundException {
        when(ur.validate("abc", "123")).thenReturn(false);

        // test
        as.authenticate("abc", "123");
    }

Note the parameter to the @Test annotation that declares the test should throw the exception.

CodePudding user response：

You are stubbing instead of asserting in your test, so basically you are not testing anything. A test should include at least one assertion, so it should look something similar to this:

assertThrows(UserNotFoundException.class, () -> as.authenticate("abc", "123"));