NullPointerException in Junit 5 @MockBean

Question

I wrote a JUnit 5 test for my service in my Spring Boot application. I used @MockBean for mock PasswordEncoder and other beans but I obtain a NullPointerException.

I always obtain a NullPointerException duraing "when" call : when(compteRepository.getByLogin(anyString())).thenReturn(Optional.of(acc));

Service

package com.compte.application.impl;

import com.compte.application.CompteService;
import com.compte.domain.exceptions.EntityNotFoundExcpetion;
import com.compte.domain.model.Compte;
import com.compte.domain.model.CompteUpdatedData;
import com.compte.domain.repository.CompteRepository;
import com.compte.domain.utils.CompteUtil;
import lombok.AllArgsConstructor;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.security.crypto.password.PasswordEncoder;

import java.time.LocalDate;
import java.util.Optional;

/**
 * @author mbint
 */
@AllArgsConstructor
public class CompteServiceImpl implements CompteService{

    private final static Logger LOGGER = LoggerFactory.getLogger(CompteService.class);

    private CompteRepository CompteRepository;
    private PasswordEncoder passwordEncoder;

    @Override
    public Optional<Compte> getByLogin(String login) {
        return CompteRepository.getByLogin(login);
    }

    @Override
    public void update(final Long id, CompteUpdatedData updatedData) {
        Optional<Compte> optional = CompteRepository.getById(id);
        if(optional.isPresent()) {
            Compte Compte = optional.get();
            Compte.setFirstName(updatedData.getFirstName());
            Compte.setLastName(updatedData.getLastName());
            CompteRepository.save(Compte);
        } else {
            throw new EntityNotFoundExcpetion("Compte: " + id + " not found !!");
        }
    }
}

Junit Test

package com.compte.application;

import com.compte.application.impl.CompteServiceImpl;
import com.compte.domain.model.Compte;
import com.compte.domain.model.CompteUpdatedData;
import com.compte.domain.repository.compteRepository;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.mock.mockito.MockBean;
import org.springframework.security.crypto.password.PasswordEncoder;

import java.util.ArrayList;
import java.util.List;
import java.util.Optional;

import static org.mockito.Mockito.*;


/**
 * @author mbint
 */
public class CompteServiceImplTest {

    private final static String PASSWORD = "Passw00rd";

    @MockBean
    private compteRepository compteRepository;
    @MockBean
    private PasswordEncoder passwordEncoder;
    private CompteService CompteService = new CompteServiceImpl(compteRepository, passwordEncoder);

    @DisplayName(("Should return existing user"))
    @Test
    private void given_login_then_return_existing_user() {
        Compte acc = Compte.builder().id(1L)
                .firstName("Luc")
                .lastName("JOJO")
                .login("xxx@gmail.com")
                .password("xxxxxxxxxxxxxxx")
                .build();
        when(compteRepository.getByLogin(anyString())).thenReturn(Optional.of(acc));

        Optional<Compte> optional = CompteService.getByLogin("xxx@gmail.com");
        Compte Compte = optional.get();

        Assertions.assertSame(1L, acc.getId());
        Assertions.assertSame("xxx@gmail.com", Compte.getLogin());
    }

    @DisplayName("Should update existing user")
    @Test
    public void given_edited_Compte_then_update_user() {
        Compte acc = Compte.builder().id(1L)
                .firstName("Luc")
                .lastName("JOJO")
                .email("xxx@gmail.com")
                .password("xxxxxxxxxxxxxxx")
                .build();
        when(compteRepository.getById(anyLong())).thenReturn(Optional.of(acc));

        CompteUpdatedData updatedData = CompteUpdatedData.builder()
                .firstName("Moos")
                .lastName("Man")
                .build();
        CompteService.update(1L, updatedData);
        Assertions.assertSame("Moos", acc.getFirstName());
    }

    private List<Compte> getComptes() {
        List<Compte> Comptes = new ArrayList<>();

        Compte acc1 = Compte.builder()
                .id(1L)
                .firstName("Luc")
                .lastName("JOJO")
                .email("xxx@gmail.com")
                .login("xxx@gmail.com")
                .build();
        Comptes.add(acc1);

        Compte acc2= Compte.builder()
                .id(2L)
                .firstName("Jean")
                .lastName("KELLY")
                .email("jean.kelly@gmail.com")
                .login("jean.kelly@gmail.com")
                .build();
        Comptes.add(acc2);

        Compte acc3= Compte.builder()
                .id(3L)
                .firstName("Marc")
                .lastName("BARBY")
                .email("marc.barby@gmail.com")
                .login("marc.barby@gmail.com")
                .build();
        Comptes.add(acc3);

        return Comptes;
    }

}

Spring boot application

package com.compte;

import com.compte.application.CompteService;
import com.compte.application.impl.CompteServiceImpl;
import com.compte.domain.repository.CompteRepository;
import com.compte.infrastructure.repository.database.CompteDBRepositiry;
import com.ombsc.bargo.common.config.SwaggerConfig;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Import;
import org.springframework.hateoas.client.LinkDiscoverer;
import org.springframework.hateoas.client.LinkDiscoverers;
import org.springframework.hateoas.mediatype.collectionjson.CollectionJsonLinkDiscoverer;
import org.springframework.plugin.core.SimplePluginRegistry;
import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
import org.springframework.security.crypto.password.PasswordEncoder;

import java.util.ArrayList;
import java.util.List;

@ComponentScan({"com.compte.interfaces.interfaces"})
@SpringBootApplication
@Import({SwaggerConfig.class})
public class CompteApplication {

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

    @Bean
    public CompteRepository getRepository() {
        return new CompteDBRepositiry();
    }

    @Bean
    public PasswordEncoder passwordEncoder() {
        return new BCryptPasswordEncoder();
    }


    @Bean
    public CompteService CompteService(CompteRepository repository, PasswordEncoder passwordEncoder) {
        return new CompteServiceImpl(repository, passwordEncoder);
    }

    @Bean
    public LinkDiscoverers discovers() {
        List<LinkDiscoverer> plugins = new ArrayList<>();
        plugins.add(new CollectionJsonLinkDiscoverer());
        return new LinkDiscoverers(SimplePluginRegistry.create(plugins));
    }
}

Answer 1

The mocks need to be initialized before they can be used. There are several options to do this.

The first option would be to use @SpringExtension which will initialize the mocks annotated with @MockBean :

@ExtendWith(SpringExtension.class)
public class CompteServiceImplTest {
    @Autowired
    private CompteService CompteService;

    @MockBean
    private compteRepository compteRepository;

    // ...
}

This will make sure that the repository bean is mocked before the service bean is autowired.

However, since you are writing a unit test for the service, you don't need the Spring extension at all. The second option is to use @Mock instead of @MockBean , and call @InjectMocks in conjunction with the MockitoExtension for constructing the service under test:

@ExtendWith(MockitoExtension.class)
public class CompteServiceImplTest {
    @InjectMocks
    private CompteService CompteService;
    @Mock
    private compteRepository compteRepository;

    // ...
}

Alternatively, you could just call MockitoAnnotations.initMocks() , which will initialize the mocks annotated with @Mock , and use constructor injection for your service:

public class CompteServiceImplTest {
    private CompteService CompteService;

    @Mock
    private compteRepository compteRepository;

    @BeforeEach
    void setUp() {
        MockitoAnnotations.initMocks(this);
        CompteService = new CompteServiceImpl(compteRepository, ...);
    }

    // ...
}

Finally, you could do it all without annotations just by calling Mockito.mock() directly:

public class CompteServiceImplTest {
    private compteRepository compteRepository;

    @BeforeEach
    void setUp() {
        compteRepository = Mockito.mock();
        CompteService = new CompteServiceImpl(compteRepository, ...);
    }

    // ...
}