LibTest/async/Stream/reduce_A01_t03.dart

/*
 * Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 * for details. All rights reserved. Use of this source code is governed by a
 * BSD-style license that can be found in the LICENSE file.
 */
/**
 * @assertion Future<T> reduce(T combine(T previous, T element))
 * Reduces a sequence of values by repeatedly applying combine.
 * @description Checks that if the stream contains no elements, the combine method
 * is not called and the future returns an error.
 * @note undocumented
 * @author kaigorodov
 */

import "dart:async";
import "../../../Utils/async_utils.dart";
import "../../../Utils/expect.dart";

void check(Iterable data, combine(previous, var element)) {
  Stream s=new Stream.fromIterable(data);
  asyncStart();
  Future f=s.reduce(combine);
    f.then((value){
      Expect.fail("unexpected call to onValue($value)");
    },
    onError: (Object error){
      asyncEnd();
    }
  );
}

main() {
  check([], null);
}