Mockito rest template is always null for mocked object

Question

When mocking a class which contains a rest template, the rest template is always null, my code is:

public class ClassA {

    private final RestTemplate restTemplate;

    public ClassA(RestTemplate restTemplate) {
        this.restTemplate = restTemplate;
    }

    public byte[] method(String url) {
       // do some restTemplate.getForObject()
    }
}

   @RunWith(SpringRunner.class)
   @SpringBootTest(classes = {Application.class})
public class TestClass {

    @Mock
    private ClassA classa

     public void test1() {

      Mockito.doReturn(byeArray).when(classA).method("url");
     }
}

When inspecting the line Mockito.doReturn(byeArray).when(classA).method("url"); i notice that the object classA contains the rest template but it is null.

Answer 1

Mocking is done on dependencies, not on the class under test. there are ways to mock on the class under test methods also, that can be done using Spy .

In your current case, it should be like this.

@RunWith(SpringRunner.class)
@SpringBootTest(classes = {Application.class})
public class TestClass {

    @InjectMock
    private ClassA classa

    @Mock
    private RestTemplate restTemplate

    @Test
    public void test1() {
      Mockito.doReturn(byeArray).when(restTemplate).method(url);
   }
}

Class under test ClassA should be annotated with @InjectMocks and dependencies should be mocked using @Mock .

Another thing to note, in your test case, you should call ClassA method which needs to be tested.

@Test
public void test1() {
  Mockito.doReturn(byeArray).when(restTemplate).doSomething(url);

  classa.method(url);
}