Spring Response Object to Json String in a Unit-Test

Question

I have a spring boot rest controller which returns an object. Something like this:

@RestController
@RequestMapping("books-rest")
public class SimpleBookRestController {
    
    @GetMapping("/{id}", produces = "application/json")
    public ResponseEntity<Book> getBook(@PathVariable int id) {
        return findBookById(id);
    }
 
    
}

I have a unit test that tests this controller method (mockito mocking the service calls inside). Something like:

@RunWith(MockitoJUnitRunner.Silent.class)
public class SimpleBookRestControllerTest {

    @Autowired
    @InjectMocks
    private SimpleBookRestController simpleBookRestController;
    @Mock
    private MyService myservice;

I want now to test what spring exactly does with the object being deserialized to a JSON string. In my test, I just test the objects, which is fine. But I have now a bug which I want to see the JSON string in a unit test.

How would you do that?

Answer 1

You'll need more than a simple unit test -- the SimpleBookRestController does not handle the conversion to JSON, so you can't just unit test it.

See this guide: https://spring.io/guides/gs/testing-web/, or look for examples of using @WebMvcTest, which is a way to test the whole web layer, including REST calls and their responses.