### Question:
RestUserDetailsService implements UserDetailsManager { @Override public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException { return restTemplate.getForObject("/{0}", User.class, username); } RestUserDetailsService(RestTemplateBuilder builder,
                                  @Value("${app.service.url.users}") String rootUri); @Override UserDetails loadUserByUsername(String username); @Override void createUser(UserDetails userDetails); @Override void updateUser(UserDetails userDetails); @Override void deleteUser(String username); @Override void changePassword(String username, String password); @Override boolean userExists(String username);  }### Answer:
@Test public void testLoadUserByUsername() { server.expect(requestTo("/" + USERNAME)).andExpect(method(GET)) .andRespond(withHalJsonResponse("/user_jbloggs_GET.txt")); UserDetails userDetails = service.loadUserByUsername(USERNAME); assertNotNull(userDetails); }