LibTest/async/StreamController/hasListener_A01_t01.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.

// @dart = 2.9

/// @assertion bool hasListener
/// Whether there is a subscriber on the Stream.
/// @description Checks that the property returns correct value.
/// @author kaigorodov


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

main() {
  StreamController controller = new StreamController();
  Stream s = controller.stream;
  Expect.isFalse(controller.hasListener);

  List events1 = new List();
  StreamSubscription ss = s.listen((event) {events1.add(event);});
  Expect.isTrue(controller.hasListener);

  ss.cancel();
  Expect.isFalse(controller.hasListener);

  controller.close();
}