@Test(expectedExceptions = UnsupportedOperationException.class)
public void fieldsShouldBeImmutable() {

  // given
  RankableObjectWithFields r = new RankableObjectWithFields(ANY_OBJECT, ANY_COUNT, ANY_FIELD);
  // when
  List<Object> fields = r.getFields();
  // try to modify the list, which should fail
  fields.remove(0);
  // then (exception)
}