Getting null pointer error testing createUser with JUnit and Mockito in RestController

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ish fady

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Feb 17, 2021, 6:01:46 AM2/17/21
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Hi

I am new Spring boots, JUnit 5 and Mockito.
I am trying to learn this technolgy.
I have simple RestController with one method createUser.
When I test this controller method through Postman, it work fine.
But when run unit test (Shown below), I am getting NullPointerException (marked inside method).
It is not creating userResponse. Here is the code;

Please can someone advice me where I am going wrong.

@RestController
@RequestMapping("/user")
public class UserRestController {
@Autowired
UserService userService;

@PostMapping(path="save", consumes= {MediaType.APPLICATION_JSON_VALUE}, produces= {MediaType.APPLICATION_JSON_VALUE})
public String createUser(@RequestBody User user) {
User userResponse = userService.createUser(user);
System.out.println("userResponse ..: " + userResponse );  // These is null when Test run
return String.valueOf(userResponse.getId());
}
} //  end UserController


@Service
public class UserServiceImpl implements UserService {

@Autowired
private UserRepository userRepository;

@Override
public User createUser(User user) {
User userResponse = userRepository.save(user);
return userResponse;
}
}

@WebMvcTest(UserRestController.class)
public class UserRestControllerTest {
@Autowired
private MockMvc mockMvc;
@Autowired
private ObjectMapper objectMapper;
@MockBean
UserService userService;
@Test    
@DisplayName("UserRestController createUser Test")
public void createUserTest() throws JsonProcessingException, Exception {
User newUser = new User("Mr", "Dabby", "Wall", 27);
User savedUser = new User(1, "Mr", "Dabby", "Wall", 27);
when(userService.createUser(newUser)).thenReturn(savedUser);

String url = "/user/save";
this.mockMvc.perform(post(url)
.contentType(MediaType.APPLICATION_JSON)
.content(objectMapper.writeValueAsString(newUser)))
.andExpect(status().isOk())
.andExpect(content().string("1")
);
}
}

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:652)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
at org.springframework.test.web.servlet.TestDispatcherServlet.service(TestDispatcherServlet.java:72)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
at org.springframework.mock.web.MockFilterChain$ServletFilterProxy.doFilter(MockFilterChain.java:1
Caused by: java.lang.NullPointerException
at com.ics.restController.UserRestController.createUser(UserRestController.java:37)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:197)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:141)



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