### Question:
UserServiceImpl implements UserService { @Override public User findOne(String username) { User user = userRepository.findDetails(username); if (user == null) { ResultMessages messages = ResultMessages.error() .add(MessageKeys.E_CT_US_8101, username); throw new ResourceNotFoundException(messages); } return user; }  @Override User findOne(String username); @Override User findOneByUsernameOrEmail(String usernameOrEmail); @Override Page<User> findPage(Pageable pageable); @Transactional @Override User create(User user, String rawPassword); @Transactional @Override User update(String username, User updatedUser,
                       String updatedRawPassword); @Transactional @Override User updateWithoutPassword(String username, User updatedUser); @Transactional @Override void delete(String username);  }### Answer:
@Test public void testFindOne() { User user = userService.findOne("admin"); assertThat(user, is(notNullValue())); }