找不到为什么jUnit测试返回NullPointerException

Question

我有简单的Spring启动Rest应用程序从数据库返回用户列表。应用程序按预期工作但测试方案因错误而失败。经过长时间的谷歌搜索无法弄清楚为什么？似乎测试类无法访问userRepository而不是调用userRepository.getAllUsers，它调用AppController.getAllUsers。

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException
……………………………
Caused by: java.lang.NullPointerException
    at com.loan.demo.controller.AppController.getAllUsers(AppController.java:43)
 …………………………………………..

这些是我的类：LoanAppApplication

@SpringBootApplication
public class LoanAppApplication {
public static void main(String[] args) {
    SpringApplication.run(LoanAppApplication.class, args);
}
}

类User.java

@Entity
@Table(name="USERTABLE")
public class User {
private int id;
@NotNull
private String firstName;
@NotNull
private String lastName;
@NotNull
private String persID;
private int blocked;
private Set<Loan> loans;

public User() {
}
public User(String firstName, String lastName, String persID) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.persID = persID;
}

UserRepository：

@Repository
public interface UserRepository extends JpaRepository<User, Integer>{
    public User findById(int Id);
    public User findByPersID(String userId);
}

和休息控制器：

@RestController
public class AppController {

    @Autowired
    UserRepository userRepository;

    @GetMapping("/doit")
    public String doIt() {
        return "Do It";
    }

    //list all users
    @GetMapping("/users")
    public List<User> getAllUsers() {
        return userRepository.findAll(); // this is line 43 from debuging error log
    }
}

和测试类：

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = {LoanAppApplication.class})
public class LoanAppApplicationTests {

    private MockMvc mockMvc;

    @InjectMocks
    private AppController appController;

    @Before
    public void addData() {
        mockMvc = MockMvcBuilders.standaloneSetup(appController)
                .build();
    }
    //First test scenario that return only string works perfectly
    @Test
    public void testData() throws Exception {
        mockMvc.perform(get("/doit")
                )
        .andExpect(status().isOk())
        .andExpect(content().string("Do It"));
    }
    //but second that should return empty json string fails with exception
    @Test
    public void testGet() throws Exception {
        mockMvc.perform(get("/users")
                )
        .andExpect(status().isOk())
        .andExpect(content().string("Do It")); //this test should fail but not return exception
    }
}

Answer 1

您需要模拟您的userRepository

@Mock
UserRepository userRepository;

所以在@Mock之后你需要在@Before中初始化Mock`s，添加：

MockitoAnnotations.initMocks(this);

然后在代码设置中，您想要获得哪些用户

User user = new User();
when(userRepository.getUsers()).thenReturn(Collections.singletonList(user));

然后检查

verify(userRepository, times(1)).getUsers();
verifyNoMoreInteractions(userRepository);

这是因为您的应用程序上下文不起作用