Post entity returning null for testresttemplate - resttemplate

Question

I am doing my integration test using test rest template but for postForEntity method I am getting null as response body, but I saw examples which were working fine on that but I am unable to resolve my issue,
PFB my test case
#RunWith(SpringRunner.class)
#SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
#ActiveProfiles("test")
public class PersonControllerTests {
#Autowired
private TestRestTemplate restTemplate;
#MockBean
private PersonRepository mockRepository;
#Before
public void init() {
List<Person> list = new ArrayList<>();
Person p1 = new Person("dumm1", "lastName1",22);
Person p2 = new Person("dumm2", "lastName2",32);
p1.setId(1l);
list.add(p2);
list.add(p1);
when(mockRepository.findAll()).thenReturn(list);
when(mockRepository.findById(1l)).thenReturn(Optional.of( p1 ));
}
#Test
public void createPerson() throws Exception {
Person p = new Person("dummy1", "dumm2", 11);
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);
HttpEntity<Person> httpEntity = new HttpEntity<Person>(p,headers);
ResponseEntity<String> response = restTemplate
.withBasicAuth("user", "password")
.postForEntity("/persons/create", httpEntity, String.class);
assertEquals(HttpStatus.OK, response.getStatusCode());
//assertEquals(MediaType.APPLICATION_JSON, response.getHeaders().getContentType());
assertEquals(11, response.getBody());
}
PFB my original code:
#RestController
#RequestMapping("/persons")
public class PersonController {
#Autowired
PersonRepository personRepository;
#GetMapping("/all")
public Iterable<Person> getAllUser() {
return personRepository.findAll();
}
#PostMapping(value ="/create",consumes = MediaType.APPLICATION_JSON_VALUE)
public Person createUser( #RequestBody Person person) {
return personRepository.save(person);
}
}
I believe I am doing some silly mistake but unable to understand

Answer 1

You are using #MockBean for your PersonRepository. Without any stubbing setup, Mockito returns null for reference types.
That's why return personRepository.save(person); returns null during your test.
You can stub your mock to simulate its behavior:
// import static org.mockito.ArgumentMatchers.any;
when(personRepository.save(ArgumentMatchers.any(Person.class))).thenAnswer(invocation -> {
Person person = invocation.getArgument(0);
// I assume you have an id field
person.setId(42L);
return person;
});