Mock test for Login Controller throwing null pointer exception for AuthenticationManager

Question

I have an error when I try to create a post request in my Mock test. It tells me that the authenticationManager is null(meaning it wasn't autowired).

I have a Login Controller having an autowired AuthenticationManager with three methods(login/register/userinfo) .

I tried to create a Login Controller Test with an instance of LoginController having injectedMocks but I don't know how to use it(I am not accustomed to testing).

Login Controller

@RestController
@RequestMapping("/auth")
@CrossOrigin
public class LoginController {

    @Autowired
    private AuthenticationManager authenticationManager;

    @Autowired
    JWTTokenHelper jWTTokenHelper;

    @Qualifier("myUserDetails")
    @Autowired
    private UserDetailsService userDetailsService;

    String jwtToken;

    private final UserService userService;

    @Autowired
    LoginController(UserService userService){
        this.userService = userService;
    }

    @PostMapping(value = "/register",consumes = "application/json")
    public ResponseEntity<?> register(@RequestBody RegistrationDTO registrationDTO) throws InvalidKeySpecException, NoSuchAlgorithmException {
        return this.login(new AuthenticationDTO(registrationDTO.getEmail(), registrationDTO.getPassword()));
    }

    @PostMapping(value = "/login",consumes = "application/json")
    public ResponseEntity<?> login(@RequestBody AuthenticationDTO authenticationDTO) throws InvalidKeySpecException, NoSuchAlgorithmException {
        System.out.print("\n" + authenticationDTO.getEmail() + "  " + authenticationDTO.getPassword() + "\n");
        final Authentication authentication = authenticationManager.authenticate(new UsernamePasswordAuthenticationToken(
                authenticationDTO.getEmail(), authenticationDTO.getPassword()));

        SecurityContextHolder.getContext().setAuthentication(authentication);

        UserDetails userDetails=(UserDetails) authentication.getPrincipal();
        String jwtToken=jWTTokenHelper.generateToken(userDetails.getUsername());
        this.jwtToken = jwtToken;
        LoginResponseDTO responseDTO = new LoginResponseDTO(jwtToken);


        //try to find out if it's a customer or not

        return ResponseEntity.ok(responseDTO);
    }


    @GetMapping("/userinfo")
    @ResponseBody
    public ResponseEntity<?> getUserInfo(Principal user){
        User userObj = (User)userDetailsService.loadUserByUsername(user.getName());

        UserDTO userInfo = new UserDTO(userObj.getId(),userObj.getName(),userObj.getEmail(),userObj.getAuthorities().toArray());


        return ResponseEntity.ok(userInfo);

    }

}

Login Controller Test

import com.example.demo.Controller.LoginController;
import com.example.demo.Model.DTOs.AuthenticationDTO;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.InjectMocks;
import org.mockito.junit.MockitoJUnitRunner;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
import org.springframework.http.MediaType;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.test.web.servlet.request.MockMvcRequestBuilders;
import org.springframework.test.web.servlet.setup.MockMvcBuilders;

@AutoConfigureMockMvc
@RunWith(MockitoJUnitRunner.class)
public class LoginControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @InjectMocks
    private LoginController loginController;

    @Before
    public void setUp(){
        mockMvc = MockMvcBuilders.standaloneSetup(loginController).build();
    }

    @Test
    public void testLogin() throws Exception{
        AuthenticationDTO authenticationDTO = new AuthenticationDTO("[email protected]","Shaorma72.");
        mockMvc.perform(
                MockMvcRequestBuilders
                        .post("/auth/login")
                        .contentType(MediaType.APPLICATION_JSON)
                        .content(asJsonString(authenticationDTO))
//                        .accept(MediaType.APPLICATION_JSON)
                )
                .andReturn();

    }

    public static String asJsonString(final Object obj) {
        try {
            return new ObjectMapper().writeValueAsString(obj);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

ERROR CONSOLE

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:681)
    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:764)
    at org.springframework.mock.web.MockFilterChain$ServletFilterProxy.doFilter(MockFilterChain.java:167)
    at org.springframework.mock.web.MockFilterChain.doFilter(MockFilterChain.java:134)
    at org.springframework.test.web.servlet.MockMvc.perform(MockMvc.java:199)
    at com.example.demo.ControllerTest.LoginControllerTest.testLogin(LoginControllerTest.java:38)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
    at org.mockito.internal.runners.DefaultInternalRunner$1$1.evaluate(DefaultInternalRunner.java:55)
    at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
    at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
    at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
    at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
    at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
    at org.mockito.internal.runners.DefaultInternalRunner$1.run(DefaultInternalRunner.java:100)
    at org.mockito.internal.runners.DefaultInternalRunner.run(DefaultInternalRunner.java:107)
    at org.mockito.internal.runners.StrictRunner.run(StrictRunner.java:41)
    at org.mockito.junit.MockitoJUnitRunner.run(MockitoJUnitRunner.java:163)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:220)
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:53)
Caused by: java.lang.NullPointerException
    at com.example.demo.Controller.LoginController.login(LoginController.java:59)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at