Mockito.when is giving random results - spring-boot

Question

I'm trying to test this changePassword method from my service class:
#Service
public class UserService {
private final UserRepository userRepository;
private final PasswordEncoder passwordEncoder;
private final BCryptPasswordEncoder bCryptPasswordEncoder;
public UserService(UserConverter userConverter, UserRepository userRepository,
PasswordEncoder passwordEncoder, BCryptPasswordEncoder bCryptPasswordEncoder) {
this.userConverter = userConverter;
this.userRepository = userRepository;
this.passwordEncoder = passwordEncoder;
this.bCryptPasswordEncoder = bCryptPasswordEncoder;
}
public User changePassword(String email, String oldPassword, String newPassword, String modifiedBy) {
User foundUser = userRepository.findByEmail(email).orElse(null);
if (Objects.isNull(foundUser)) {
String errorMessage = String.format("User lookup failed for the email '%s'", email);
logger.warn(errorMessage);
throw new EntityNotFoundException(errorMessage);
}
if (!passwordEncoder.matches(oldPassword, foundUser.getPassword())) {
String errorMessage = "Old password doesn't match";
logger.warn(errorMessage);
throw new ResponseStatusException(HttpStatus.BAD_REQUEST, errorMessage);
}
foundUser.setPassword(bCryptPasswordEncoder.encode(newPassword));
foundUser.setModifiedBy(modifiedBy);
return userRepository.save(foundUser);
} // Plus other unrelated methods
And my test class is as follows:
#ExtendWith(MockitoExtension.class)
public class UserServiceTest {
#Mock
private UserRepository userRepository;
#Mock
private UserConverter userConverter;
#Mock
private PasswordEncoder passwordEncoder;
#Mock
private BCryptPasswordEncoder bCryptPasswordEncoder;
#InjectMocks
private UserService userService;
#Test
public void changePasswordSuccessfully() throws Exception {
String email = "bojack#bojack.com";
String oldPassword = "Bojack1234";
String newPassword = "Bojack12345";
String modifiedBy = "peanutbutter#hollywoo.com";
User userToBeReturned = new User();
userToBeReturned.setPassword(newPassword);
userToBeReturned.setModifiedBy(modifiedBy);
doReturn(Optional.ofNullable(genericUser))
.when(userRepository).findByEmail(anyString());
doReturn(userToBeReturned)
.when(userRepository).save(any(User.class));
when(passwordEncoder.matches(anyString(), anyString())).thenReturn(true);
when(bCryptPasswordEncoder.encode(anyString())).thenReturn(newPassword);
User returnedUser = userService.changePassword(email, oldPassword, newPassword, modifiedBy);
assertEquals(userToBeReturned.getModifiedBy(), returnedUser.getModifiedBy());
assertEquals(userToBeReturned.getPassword(), returnedUser.getPassword());
}
#Test
public void oldPasswordDoesNotMatchWhenChangingPassword() throws Exception {
String email = "bojack#bojack.com";
String oldPassword = "Bojack1234";
String newPassword = "Bojack12345";
String modifiedBy = "peanutbutter#hollywoo.com";
User userToBeReturned = new User();
userToBeReturned.setPassword(newPassword);
userToBeReturned.setModifiedBy(modifiedBy);
doReturn(Optional.ofNullable(genericUser))
.when(userRepository).findByEmail(anyString());
assertThrows(ResponseStatusException.class, () -> {
userService.changePassword(email, oldPassword, newPassword, modifiedBy);
});
} // Plus other tests unrelated to the method that I'm testing
}
And it indeed works, but randomly, I test my whole test package and sometimes all tests pass but sometimes changePasswordSuccessfully fails on this line from UserService.java because it goes inside the if, which I'm trying to avoid
if (!passwordEncoder.matches(oldPassword, foundUser.getPassword())) {
It seems as if the when(passwordEncoder.matches(anyString(), anyString())).thenReturn(true); is not being respected, I've also tried with doReturn but to no avail.
Relevant error:
org.springframework.web.server.ResponseStatusException: 400 BAD_REQUEST "Old password doesn't match"
at cr.lasbrumas.lasbrumassource.user.UserService.changePassword(UserService.java:62)
at cr.lasbrumas.lasbrumassource.user.UserServiceTest.changePasswordSuccessfully(UserServiceTest.java:128)
Also this is how I'm cresting the bean
#Bean
public PasswordEncoder passwordEncoder() {
return PasswordEncoderFactories.createDelegatingPasswordEncoder();
}

Answer 1

I found the answer, I don't know what the formal name for this is called but apparently since I was also creating a bean of bCryptPasswordEncoder and I was also mocking it and mocking the response of bCryptPasswordEncoder.encode in the same test, it was "shadowing" the mock of PasswordEncoder, therefore it invalidated the mock for the .matches method randomly. I would guess that this happens since bCryptPasswordEncoder is an implementation of the PasswordEncoder interface.
Though there's no need for using bCryptPasswordEncoder in my case, since PasswordEncoder.encode uses bcrypt as the default.