Ensure timers are started before awaits in tests (dart-lang/stream_transform#29)

Fixes dart-lang/stream_transform#25

These tests were relying on a 5ms Timer getting started asynchronously
and firing before a 10ms delay which is not guaranteed. By waiting an
extra cycle through the event loop to ensure that the Timer starts
before the delay we can have a better guarantee of ordering.

- Add a test util to wait for Timers to start and then elapse.
- Replace `await new Future.delayed(arbitraryDelay)` with the new utility.
- Add missing copyright notices on touched files.

pkgs/stream_transform/test/audit_test.dart

diff --git a/pkgs/stream_transform/test/audit_test.dart b/pkgs/stream_transform/test/audit_test.dart
index a3b2fef..b61a8db 100644
--- a/pkgs/stream_transform/test/audit_test.dart
+++ b/pkgs/stream_transform/test/audit_test.dart
@@ -1,7 +1,14 @@
+// Copyright (c) 2017, 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.
+
 import 'dart:async';
+
 import 'package:test/test.dart';
 import 'package:stream_transform/stream_transform.dart';
 
+import 'utils.dart';
+
 void main() {
   var streamTypes = {
     'single subscription': () => new StreamController(),
@@ -47,15 +54,15 @@
           values.add(1);
           values.add(2);
           await values.close();
-          await new Future.delayed(const Duration(milliseconds: 10));
+          await waitForTimer(5);
           expect(emittedValues, [2]);
         });
 
         test('outputs multiple values spaced further than duration', () async {
           values.add(1);
-          await new Future.delayed(const Duration(milliseconds: 10));
+          await waitForTimer(5);
           values.add(2);
-          await new Future.delayed(const Duration(milliseconds: 10));
+          await waitForTimer(5);
           expect(emittedValues, [1, 2]);
         });
 
@@ -63,17 +70,17 @@
           values.add(1);
           await values.close();
           expect(isDone, false);
-          await new Future.delayed(const Duration(milliseconds: 10));
+          await waitForTimer(5);
           expect(isDone, true);
         });
 
         test('closes output if there are no pending values', () async {
           values.add(1);
-          await new Future.delayed(const Duration(milliseconds: 10));
+          await waitForTimer(5);
           values.add(2);
           await values.close();
           expect(isDone, false);
-          await new Future.delayed(const Duration(milliseconds: 10));
+          await waitForTimer(5);
           expect(isDone, true);
         });
 
@@ -84,7 +91,8 @@
           values.add(2);
           await new Future.delayed(const Duration(milliseconds: 3));
           values.add(3);
-          expect(emittedValues, [2]);
+          await waitForTimer(5);
+          expect(emittedValues, [2, 3]);
         });
 
         if (streamType == 'broadcast') {
@@ -93,7 +101,7 @@
             transformed.listen(otherValues.add);
             values.add(1);
             values.add(2);
-            await new Future.delayed(const Duration(milliseconds: 10));
+            await waitForTimer(5);
             expect(emittedValues, [2]);
             expect(otherValues, [2]);
           });

pkgs/stream_transform/test/debounce_test.dart

diff --git a/pkgs/stream_transform/test/debounce_test.dart b/pkgs/stream_transform/test/debounce_test.dart
index a28d2ca..59cb809 100644
--- a/pkgs/stream_transform/test/debounce_test.dart
+++ b/pkgs/stream_transform/test/debounce_test.dart
@@ -1,7 +1,14 @@
+// Copyright (c) 2017, 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.
+
 import 'dart:async';
+
 import 'package:test/test.dart';
 import 'package:stream_transform/stream_transform.dart';
 
+import 'utils.dart';
+
 void main() {
   var streamTypes = {
     'single subscription': () => new StreamController(),
@@ -47,21 +54,21 @@
           values.add(1);
           values.add(2);
           await values.close();
-          await new Future.delayed(const Duration(milliseconds: 10));
+          await waitForTimer(5);
           expect(emittedValues, [2]);
         });
 
         test('outputs multiple values spaced further than duration', () async {
           values.add(1);
-          await new Future.delayed(const Duration(milliseconds: 10));
+          await waitForTimer(5);
           values.add(2);
-          await new Future.delayed(const Duration(milliseconds: 10));
+          await waitForTimer(5);
           expect(emittedValues, [1, 2]);
         });
 
         test('waits for pending value to close', () async {
           values.add(1);
-          await new Future.delayed(const Duration(milliseconds: 10));
+          await waitForTimer(5);
           await values.close();
           await new Future(() {});
           expect(isDone, true);
@@ -69,12 +76,12 @@
 
         test('closes output if there are no pending values', () async {
           values.add(1);
-          await new Future.delayed(const Duration(milliseconds: 10));
+          await waitForTimer(5);
           values.add(2);
           await new Future(() {});
           await values.close();
           expect(isDone, false);
-          await new Future.delayed(const Duration(milliseconds: 10));
+          await waitForTimer(5);
           expect(isDone, true);
         });
 
@@ -84,7 +91,7 @@
             transformed.listen(otherValues.add);
             values.add(1);
             values.add(2);
-            await new Future.delayed(const Duration(milliseconds: 10));
+            await waitForTimer(5);
             expect(emittedValues, [2]);
             expect(otherValues, [2]);
           });
@@ -100,7 +107,7 @@
           values.add(1);
           values.add(2);
           await values.close();
-          await new Future.delayed(const Duration(milliseconds: 10));
+          await waitForTimer(5);
           expect(emittedValues, [
             [1, 2]
           ]);
@@ -109,9 +116,9 @@
         test('separate lists for multiple values spaced further than duration',
             () async {
           values.add(1);
-          await new Future.delayed(const Duration(milliseconds: 10));
+          await waitForTimer(5);
           values.add(2);
-          await new Future.delayed(const Duration(milliseconds: 10));
+          await waitForTimer(5);
           expect(emittedValues, [
             [1],
             [2]
@@ -124,7 +131,7 @@
             transformed.listen(otherValues.add);
             values.add(1);
             values.add(2);
-            await new Future.delayed(const Duration(milliseconds: 10));
+            await waitForTimer(5);
             expect(emittedValues, [
               [1, 2]
             ]);

pkgs/stream_transform/test/throttle_test.dart

diff --git a/pkgs/stream_transform/test/throttle_test.dart b/pkgs/stream_transform/test/throttle_test.dart
index 10a34fd..94e1851 100644
--- a/pkgs/stream_transform/test/throttle_test.dart
+++ b/pkgs/stream_transform/test/throttle_test.dart
@@ -1,7 +1,14 @@
+// Copyright (c) 2017, 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.
+
 import 'dart:async';
+
 import 'package:test/test.dart';
 import 'package:stream_transform/stream_transform.dart';
 
+import 'utils.dart';
+
 void main() {
   var streamTypes = {
     'single subscription': () => new StreamController(),
@@ -47,21 +54,21 @@
           values.add(1);
           values.add(2);
           await values.close();
-          await new Future.delayed(const Duration(milliseconds: 10));
+          await waitForTimer(5);
           expect(emittedValues, [1]);
         });
 
         test('outputs multiple values spaced further than duration', () async {
           values.add(1);
-          await new Future.delayed(const Duration(milliseconds: 10));
+          await waitForTimer(5);
           values.add(2);
-          await new Future.delayed(const Duration(milliseconds: 10));
+          await waitForTimer(5);
           expect(emittedValues, [1, 2]);
         });
 
         test('closes output immediately', () async {
           values.add(1);
-          await new Future.delayed(const Duration(milliseconds: 10));
+          await waitForTimer(5);
           values.add(2);
           await values.close();
           expect(isDone, true);

pkgs/stream_transform/test/utils.dart

diff --git a/pkgs/stream_transform/test/utils.dart b/pkgs/stream_transform/test/utils.dart
new file mode 100644
index 0000000..4e38ef7
--- /dev/null
+++ b/pkgs/stream_transform/test/utils.dart
@@ -0,0 +1,11 @@
+// Copyright (c) 2017, 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.
+
+import 'dart:async';
+
+/// Cycle the event loop to ensure timers are started, then wait for a delay
+/// longer than [milliseconds] to allow for the timer to fire.
+Future waitForTimer(int milliseconds) =>
+    new Future(() {/* ensure Timer is started*/}).then((_) =>
+        new Future.delayed(new Duration(milliseconds: milliseconds + 1)));