code: public static <T> Predicate<T> spyRes(Predicate<T> predicate, Box<Boolean> result) {
          return spy(predicate, result, Box.<T>empty());
      }
docs: Proxies a predicate spying for result.
  
  @param <T> the predicate parameter type
  @param predicate the predicate that will be spied
  @param result a box that will be containing spied result
  @return the proxied predicate