如何模拟 REST 模板交换？

我有一项服务，我需要通过休息向外部服务器询问一些信息：

public class SomeService {

    public List<ObjectA> getListofObjectsA() {
        List<ObjectA> objectAList = new ArrayList<ObjectA>();
        ParameterizedTypeReference<List<ObjectA>> typeRef = new ParameterizedTypeReference<List<ObjectA>>() {};
        ResponseEntity<List<ObjectA>> responseEntity = restTemplate.exchange("/objects/get-objectA", HttpMethod.POST, new HttpEntity<>(ObjectAList), typeRef);
        return responseEntity.getBody();
    }
}

我如何编写 JUnit 测试getListofObjectsA()?

我尝试过以下方法：

@RunWith(MockitoJUnitRunner.class)
public class SomeServiceTest {
    private MockRestServiceServer mockServer;

    @Mock
    private RestTemplate restTemplate;

    @Inject
   private SomeService underTest;

@Before
public void setup() {
    mockServer = MockRestServiceServer.createServer(restTemplate);
    underTest = new SomeService(restTemplate);
    mockServer.expect(requestTo("/objects/get-objectA")).andExpect(method(HttpMethod.POST))
            .andRespond(withSuccess("{json list response}", MediaType.APPLICATION_JSON));
}

    @Test
    public void testGetObjectAList() {
    List<ObjectA> res = underTest.getListofObjectsA();
    Assert.assertEquals(myobjectA, res.get(0));
}

然而上面的代码不起作用，它表明responseEntitty is null。我怎样才能纠正我的测试以正确模拟restTemplate.exchange?

这是一个未弃用的示例参数匹配器 https://static.javadoc.io/org.mockito/mockito-core/2.2.7/org/mockito/ArgumentMatchers.html class

when(restTemplate.exchange(
                ArgumentMatchers.anyString(),
                ArgumentMatchers.any(HttpMethod.class),
                ArgumentMatchers.any(),
                ArgumentMatchers.<Class<String>>any()))
             .thenReturn(responseEntity);