Add a ScheduledStream class and some stream matchers.

pkg/scheduled_test/test/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 test_utils;
 
 import 'dart:async';
 
 import 'package:scheduled_test/scheduled_test.dart';
 import 'package:scheduled_test/src/utils.dart';
@@ skipping 40 matching lines @@
 /// Sets up a timeout for every metatest in this file.
 void setUpTimeout() {
   metaSetUp(() {
     // TODO(nweiz): We used to only increase the timeout to 10s for the Windows
     // bots, but the Linux and Mac bots have started taking upwards of 5s when
     // running pumpEventQueue, so we're increasing the timeout across the board
     // (see issue 9248).
     currentSchedule.timeout = new Duration(seconds: 10);
   });
 }
+
+/// Creates a metatest with [body] and asserts that it passes.
+///
+/// This is like [expectTestsPass], but the [test] is set up automatically.
+void expectTestPasses(String description, void body()) =>
+  expectTestsPass(description, () => test('test', body));
+
+/// Creates a metatest that runs [testBody], captures its schedule errors, and
+/// passes them to [validator].
+///
+/// [testBody] is expected to produce an error, while [validator] is expected to
+/// produce none.
+void expectTestFails(String description, void testBody(),
+    void validator(List<ScheduleError> errors)) {
+  expectTestsPass(description, () {
+    var errors;
+    test('test body', () {
+      currentSchedule.onException.schedule(() {
+        errors = currentSchedule.errors;
+      });
+
+      testBody();
+    });
+
+    test('validate errors', () {
+      expect(errors, everyElement(new isInstanceOf<ScheduleError>()));
+      validator(errors);
+    });
+  }, passing: ['validate errors']);
+}