LibTest/isolate/ReceivePort/fold_A01_t02.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 fold(initialValue, combine(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 initialValue.
/// @note undocumented
/// @author kaigorodov

import "dart:async";
import "../../../Utils/expect.dart";
import "IsolateStream.dart" as IsolateStream;

void check(
    Iterable data, initialValue, combine(previous, var element), var expected) {
  Stream s = IsolateStream.fromIterable(data);
  asyncStart();
  Future f = s.fold(initialValue, combine);
  f.then((var actual) {
    Expect.equals(expected, actual);
    asyncEnd();
  });
}

main() {
  check([], null, (p, e) {Expect.fail("combine musn't be called");}, null);
  check([], 777, (p, e) {Expect.fail("combine musn't be called");}, 777);
  check([], "", (p, e) {Expect.fail("combine musn't be called");}, "");
}