@Test
  public void updateCannotModifyGroups() {
    ScimUser jo = new ScimUser(null, "josephine", "Jo", "NewUser");
    jo.addEmail("*****@*****.**");
    jo.setGroups(Collections.singleton(new Group(null, "dash/user")));

    ScimUser joe = db.update(JOE_ID, jo);

    assertEquals(JOE_ID, joe.getId());
    assertNull(joe.getGroups());
  }