Mockito在使用模拟时抛出NullpointerException

Question

我正在尝试为Web服务创建测试用例,但我得到了nullpointerexception.这是Web服务:

@Path("friendservice")
public class FriendWebService {

private static final Logger logger = Logger.getLogger(FriendWebService.class);

@EJB
private FriendRequestServiceInterface friendRequestService;

@GET
@Path("friendrequest")
@Produces(MediaType.TEXT_PLAIN)
public String createFriendRequest(
        @Context HttpServletRequest request) {
    logger.info("createFriendRequest called");

    String result = "false";
    User user = (User) request.getSession().getAttribute("user");
    User otherUser = (User) request.getSession().getAttribute("profileuser");
    if ((user != null) && (otherUser != null)) {
        logger.info("Got two users from session, creating friend request.");
        if (friendRequestService.createFriendRequest(user, otherUser)) {
            result = "true";
        }
    }
    return result;
}

}

这是我的测试类:

public class FriendWebServiceTest {
@Mock
FriendRequestServiceInterface FriendRequestService;
@Mock
Logger mockedLogger = mock(Logger.class);
@Mock
HttpServletRequest mockedRequest = mock(HttpServletRequest.class);
@Mock
HttpSession mockedSession = mock(HttpSession.class);
@Mock
User mockedUser = mock(User.class);
@Mock
User mockedOtherUser = mock(User.class);
@InjectMocks
FriendWebService friendWebService = new FriendWebService();

@Before
public void setUp() throws Exception {

}

@Test
public void testCreateFriendRequest() throws Exception {
    when(mockedRequest.getSession()).thenReturn(mockedSession);
    when(mockedSession.getAttribute("user")).thenReturn(mockedUser);
    when(mockedSession.getAttribute("profileuser")).thenReturn(mockedOtherUser);
    when(FriendRequestService.createFriendRequest(mockedUser, mockedOtherUser)).thenReturn(true);
    assertTrue(friendWebService.createFriendRequest(mockedRequest) == "true");
}

NullPointerException发生在"when(FriendRequestService.createFriendRequest(mockedUser,mockedOtherUser)).thenReturn(true);"

我究竟做错了什么？

Answer 1

您在模拟的实例上链接方法调用:

@Mock
HttpServletRequest mockedRequest = mock(HttpServletRequest.class);

首先,您不需要同时使用@Mock注释或mock方法.像这样,你首先分配一个模拟,然后用另一个模拟替换这个实例.我建议使用注释,因为它会为模拟添加一些上下文,例如字段的名称.这可能已经导致您,NullPointerException因为您永远不会通过调用以下方式激活注释:

MockitoAnnotations.initMocks(this);

因为到目前为止你没有使用这两个措施模拟所有实例.但是,即使这样做也会导致您的例外,所以让我们继续前进.

在friendWebService.createFriendRequest(mockedRequest)您致电:

User user = (User) request.getSession().getAttribute("user");
User otherUser = (User) request.getSession().getAttribute("profileuser");

你在两个模拟中调用方法的地方,你没有指定任何行为.这些模拟默认返回null.您需要为此指定行为,例如:

when(request.getSession()).thenReturn(myMockedSession);

在执行此链式呼叫之前.基于此,您可以指定如何对此模拟实例上的调用做出反应,例如返回用户模拟.