无法运行Mockito Junit测试

Question

我对JUnit非常陌生。我写了一个简单的JUnit测试用例，它给出了NullPointerException：

@RunWith(MockitoJUnitRunner.class)
public class ControllerTest {

    @InjectMocks
    Controller control;

    @Mock 
    Service service;

    @Test
    public void postTest() throws IOException {

        //Given

        Object o = new Object();

                //initialise the object here which the service layer would return

        String a = "abcd";
        Integer b = 5;
        Mockito.when(service.Post(a,o)).thenReturn(o);

        Mono<ResponseEntity<Object>> object = control.Post(a,o);

        StepVerifier.create(object)
        .consumeNextWith(entity -> {
            assertEquals(b,entity.getBody().get());
        })
        .expectComplete();

在这种情况下，我得到一个NullPointerException。