当 controller 中的 mocking 时，总是在数组列表中返回 NullPointerException

Question

I try to make simple unit test using JUnit and Mockito in the controller. I mocked the service because it will be called by the controller. Here is the code

@RunWith(MockitoJUnitRunner.class)
class MsCustomerControllerTest {
    
    @Mock
    MsCustomerService customerServiceMock;

    
    @InjectMocks
    MsCustomerController customerController;
    
    @Test
    void test() {
        fail("Not yet implemented");
    }
    

    
    @Test
    public void findAllCustomerTest() {
        
        List<MsCustomer> listCustomer = new ArrayList<MsCustomer>();
        listCustomer.add(new MsCustomer(1, "Rosa", "Titian Indah", LocalDateTime.now()));
        listCustomer.add(new MsCustomer(2, "Rosa2", "Titian Indah2", LocalDateTime.now()));
        when(customerServiceMock.findAllCustomer()).thenReturn(listCustomer);
        
        ResponseEntity response = new ResponseEntity(listCustomer, HttpStatus.OK);
        
        
        assertEquals(response, customerController.findAllCustomer());
    }

}

note: the customerController also return response entity, so assert with response entity too.

Here is the result

I have tried other method and it also give me the NullPointerException.

Answer 1

Try adding an init method and annotate it with @BeforeEach . Then inside the method add MockitoAnnotations.initMocks(this); which initializes fields annotated with Mockito annotations.

@RunWith(MockitoJUnitRunner.class)
class MsCustomerControllerTest {
    
    @Mock
    MsCustomerService customerServiceMock;

    
    @InjectMocks
    MsCustomerController customerController;

    @BeforeEach
    void initMock() {
        MockitoAnnotations.initMocks(this);
    }
    
    @Test
    void test() {
        fail("Not yet implemented");
    }
    

    
    @Test
    public void findAllCustomerTest() {
        
        List<MsCustomer> listCustomer = new ArrayList<MsCustomer>();
        listCustomer.add(new MsCustomer(1, "Rosa", "Titian Indah", LocalDateTime.now()));
        listCustomer.add(new MsCustomer(2, "Rosa2", "Titian Indah2", LocalDateTime.now()));
        when(customerServiceMock.findAllCustomer()).thenReturn(listCustomer);
        
        ResponseEntity response = new ResponseEntity(listCustomer, HttpStatus.OK);
        
        
        assertEquals(response, customerController.findAllCustomer());
    }

}