LibTest/async/StreamIterator/current_A01_t02.dart

// Copyright (c) 2016, 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 T current
 * The current value of the stream.
 *
 * Is null before the first call to moveNext and after a call to moveNext
 * completes with a false result or an error.
 *
 * When a moveNext call completes with true, the current field holds the most
 * recent event of the stream, and it stays like that until the next call to
 * moveNext. Between a call to moveNext and when its returned future completes,
 * the value is unspecified.
 *
 * @description Checks that the property current returns null before the first
 * call to moveNext and after a call to moveNext completes with a false result.
 * @author ngl@unipro.ru
 */
import "dart:async";
import "../../../Utils/expect.dart";

main() {
  StreamController c = new StreamController();
  StreamIterator si = new StreamIterator(c.stream);

  Expect.isNull(si.current);
  c.add(1);
  Expect.isNull(si.current);

  asyncStart();
  si.moveNext().then((bool value) {
    Expect.isTrue(value);
    Expect.equals(1, si.current);

    si.moveNext().then((bool value) {
      Expect.isFalse(value);
      Expect.isNull(si.current);
      asyncEnd();
    });

  });

  c.close();
}