Add a scheduled test library.

pkg/scheduled_test/lib/src/utils.dart

+// Copyright (c) 2013, 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.
+
+library utils;
+
+import 'dart:async';
+
+/// Configures [future] so that its result (success or exception) is passed on
+/// to [completer].
+void chainToCompleter(Future future, Completer completer) {
+  future.then((value) => completer.complete(value),
+      onError: (e) => completer.completeError(e.error, e.stackTrace));
+}
+
+/// Prepends each line in [text] with [prefix].
+String prefixLines(String text, {String prefix: '| '}) =>
+  text.split('\n').map((line) => '$prefix$line').join('\n');
+
+/// Returns a [Future] that completes in [milliseconds].
+Future sleep(int milliseconds) {
+  var completer = new Completer();
+  new Timer(milliseconds, (_) => completer.complete());
+  return completer.future;
+}
+
+/// Wraps [input] to provide a timeout. If [input] completes before
+/// [milliseconds] have passed, then the return value completes in the same way.
+/// However, if [milliseconds] pass before [input] has completed, [onTimeout] is
+/// run and its result is passed to [input] (with chaining, if it returns a
+/// [Future]).
+///
+/// Note that timing out will not cancel the asynchronous operation behind
+/// [input].
+Future timeout(Future input, int milliseconds, onTimeout()) {
+  bool completed = false;
+  var completer = new Completer();
+  var timer = new Timer(milliseconds, (_) {
+    completed = true;
+    chainToCompleter(new Future.immediate(null).then((_) => onTimeout()),
+        completer);
+  });
+  input.then((value) {
+    if (completed) return;
+    timer.cancel();
+    completer.complete(value);
+  }).catchError((e) {
+    if (completed) return;
+    timer.cancel();
+    completer.completeError(e.error, e.stackTrace);
+  });
+  return completer.future;
+}