final SettableFuture<Object> toReturn = SettableFuture.create();
    AsyncFunction<Object, Object> function =
        tagged(
            "Called my toString",
            new AsyncFunction<Object, Object>() {
              @Override
              public ListenableFuture<Object> apply(Object input) throws Exception {
                return toReturn;
              }
            });

    final SettableFuture<Object> toReturn = SettableFuture.create();
    AsyncFunction<Object, Object> function =
        tagged(
            "Called my toString",
            new AsyncFunction<Object, Object>() {
              @Override
              public ListenableFuture<Object> apply(Object input) throws Exception {
                return toReturn;
              }
            });