code: public static <T1, T2> BiPredicate<T1, T2> spy1st(BiPredicate<T1, T2> predicate, Box<T1> param1) {
          return spy(predicate, Box.<Boolean>empty(), param1, Box.<T2>empty());
      }
docs: Proxies a binary predicate spying for first parameter
  
  @param <T1> the predicate first parameter type
  @param <T2> the predicate second parameter type
  @param predicate the predicate that will be spied
  @param param1 a box that will be containing the first spied parameter
  @return the proxied predicate