Using BCryptPasswordEncoder in Unit Test returns a null value

Question

I'm learning Unit Testing with JUnit and Mockito on a Spring boot application, I have a registration method I want to test, in my test method I create a User but I see that the value of the password is always null when using.encode(mypassword), resulting in an Assertion Error.

---

UserServiceImpl.java

@Service
public class UserServiceImpl implements UserService {
    private final UserRepository userRepository;
    private final PasswordEncoder passwordEncoder;

    public UserServiceImpl(UserRepository userRepository, PasswordEncoder passwordEncoder) {
        this.userRepository = userRepository;
        this.passwordEncoder = passwordEncoder;
    }


    @Override
    public User register(User user) {


         Role role = roleService.findByName(ERole.ROLE_USER);

         Set<Role> roleSet = new HashSet<>();
         user.setFullName(user.getFullName());
         user.setEmailAddress(user.getEmailAddress());
         user.setPassword(passwordEncoder.encode(user.getPassword()));
         user.setConfirmPassword("");
         user.setEmailVerified(true);
         roleSet.add(role);
         user.setRoles(roleSet);

         if(userRepository.existsByEmailAddress(user.getEmailAddress())) {
             throw new EmailAlreadyExistsException("Account already exists with this email");
         }
        return userRepository.save(user);
    }



}

---

UserServiceImplTest.java

@ExtendWith(MockitoExtension.class)
class UserServiceImplTest {

    @InjectMocks
    private UserServiceImpl userService;

    @Mock
    private UserRepository userRepository;

    @Mock
    public PasswordEncoder passwordEncoder;

  

   @BeforeEach
    void setUp() {
        userService = new UserServiceImpl(userRepository, passwordEncoder);
    }

  @Test
    void testIfUserCanRegisterSuccessfully() {

        User user = new User(1, "admin", "admin@gmail.com", passwordEncoder.encode("password"));

        when(userRepository.save(any())).thenReturn(user);
        User theUser = userService.register(user);


        System.out.println("theUser: " + theUser);

        assertNotNull(theUser);
        assertEquals(1, theUser.getId());
        assertEquals("admin@gmail.com", theUser.getEmailAddress());
        assertTrue(passwordEncoder.matches("password", theUser.getPassword()));
    }

}

---

SecurityConfig.java

@Configuration
@EnableWebSecurity
@EnableGlobalMethodSecurity(prePostEnabled = true, securedEnabled = true, jsr250Enabled = true)
public class SecurityConfig extends WebSecurityConfigurerAdapter {


    @Value("${spring.security.ant.matchers}")
    private String[] securityAntMatchers;
    

    @Autowired
    private UserDetailsServiceImpl userDetailsService;

    @Autowired
    private JwtAuthenticationEntryPoint authenticationEntryPoint;

    @Bean
    public JwtAuthenticationTokenFilter jwtAuthenticationTokenFilter() {
        return new JwtAuthenticationTokenFilter();
    }

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

    @Bean
    @Override
    public AuthenticationManager authenticationManager() throws Exception {
        return super.authenticationManager();
    }


    @Override
    protected void configure(AuthenticationManagerBuilder auth) throws Exception {
        auth.userDetailsService(userDetailsService).passwordEncoder(passwordEncoder());
    }



    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
            .csrf().disable().formLogin().disable().httpBasic().disable();

        http
            .sessionManagement()
            .sessionCreationPolicy(SessionCreationPolicy.STATELESS)
            .and()
            .exceptionHandling().authenticationEntryPoint(authenticationEntryPoint)
            .and()
            .addFilterBefore(jwtAuthenticationTokenFilter(), UsernamePasswordAuthenticationFilter.class);

        http
            .authorizeRequests()
            .antMatchers(securityAntMatchers)
            .permitAll()
            .anyRequest()
            .authenticated();
    }

}

---

The output of theUser is this, I'm not sure how to handle the password encryption when testing the method.

theUser: User{id=1, fullName='admin', emailAddress='admin@gmail.com', dateJoined=Tue Nov 15 00:06:01 CAT 2022, emailVerified=true, password='null'}

---

EDITED

    @BeforeEach
    void setUp() {
        // Instantiating password encoder before every test, now I get the output
        this.passwordEncoder = new BCryptPasswordEncoder();
        userService = new UserServiceImpl(userRepository, passwordEncoder);


    }

  @Test
    void testIfUserCanRegisterSuccessfully() {
        User user = new User(1, "admin", "admin@gmail.com","password");

        when(userRepository.save(any())).thenReturn(user);
        User created = userService.register(user);

        assertEquals(created.getPassword(), user.getPassword());
        assertEquals(created.getEmailAddress(), user.getEmailAddress());
        verify(userRepository).save(any());
    }

Answer 1

Your services in the tests:

    @Mock
    private UserRepository userRepository;

    @Mock
    public PasswordEncoder passwordEncoder;

Are mocks, which means they won't actually do anything unless you explicitly tell them what to do by stubbing methods, as you do here:

       when(userRepository.save(any())).thenReturn(user);

The issue is that you haven't stubbed any methods in the passwordEncoder so it's methods will do nothing and return null .

Also, it appears you are encoding your password twice (once in the test and once in the register method), which could lead to errors down the line even with proper stubbing