Using #InjectMock giving URI not absolute error - spring-boot

Question

I have written following Junit for the method which is using rest template to call another service but the mocking is throwing URI not absolute error.
Method:
#Value("${app.prop.esso-url}")
private String essoUrl;
public ResponseEntity<String> essoCall(String token) {
ResponseEntity<String> response=null;
RestTemplate restTemplate = new RestTemplate();
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);
headers.add("Accept", MediaType.APPLICATION_JSON_VALUE);
headers.setBearerAuth(token);
HttpEntity<String> entity = new HttpEntity<>(headers);
response= restTemplate.exchange(essoUrl, HttpMethod.GET, entity,String.class);
logger.info("successfully received response.");
return response;
}
Junit:
#Autowired
private ObjectMapper objectMapper;
#InjectMocks
SecurityMsServiceImpl securityservice=new SecurityMsServiceImpl();
#Value("${app.prop.esso-url}")
private String essoUrl;
#Mock
private RestTemplate restTemplate;
#Test
void givenMockingIsDoneByMockito_whenGetIsCalled_shouldReturnMockedObject() {
ResponseEntity<String> responseEntity = new ResponseEntity<String>("success", HttpStatus.OK);
Mockito
.when(restTemplate.getForEntity(essoUrl
, String.class))
.thenReturn(responseEntity);
ResponseEntity<String> finalresponse=securityservice.essoCall("abc");
assertEquals(responseEntity, finalresponse);
}

Answer 1

I see this problem time and time again:
You are constructing new instance of RestTemplate in your method under test.
What you should do instead is to inject it into your bean, which means:
add a field of type RestTemplate in your bean
initialize it in constructor
in tests, pass in mocked instance
in prod, pass in a regular instance via Spring DI
RestTemplate is thread-safe and one instance of it is perfectly valid.
See Is RestTemplate thread safe?
On top of that:
my advice is to use constructor injection instead of field injection
you are mixing Spring's #Autowired with Mockito's #InjectMocks. Choose if you want to test with MockitoExtension or SpringExtension and pick the appropriate set of annotations to initialize your SUT.