More tests for async* functions

tests/language/async_star_no_cancel_test.dart

Index: tests/language/async_star_no_cancel_test.dart
diff --git a/tests/language/async_star_no_cancel_test.dart b/tests/language/async_star_no_cancel_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..da63a5d902c3401af08555bec7797948329ed00e
--- /dev/null
+++ b/tests/language/async_star_no_cancel_test.dart
@@ -0,0 +1,48 @@
+// 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.
+
+import "dart:async";
+import "package:expect/expect.dart";
+import "package:async_helper/async_helper.dart";
+
+var events = [];
+
+ticker() async* {
+  var sc;
+  var sentTickCount = 0;
+  sc = new StreamController(onListen: () {
+    events.add("listen");
+  }, onCancel: () {
+    events.add("cancel");
+  });
+
+  try {
+    var counter = 0;
+    await for (var tick in sc.stream) {
+      counter++;
+    }
+  } finally {
+    events.add("finally");
+  }
+}
+
+void main() {
+  asyncStart();
+  events.add("main");
+  final subscription = ticker().listen((val) { });
+
+  bool cancelFinished = false;
+  // Cancel the subscription.
+  // The async* function is blocked on an `await` (the inner stream) and won't
+  // be able to complete.
+  Timer.run(() {
+    subscription.cancel().then((_) => cancelFinished = true);

[hausner, 2016/02/10 21:13:17]

Maybe add and event here that proves that the subscription was cancelled. Then
check for it below. That will catch if callbacks are not executed in the
expected order. 

[floitsch, 2016/02/11 13:53:26]

Done.

+  });
+
+  new Timer(const Duration(milliseconds: 100), () {
+    Expect.isFalse(cancelFinished);
+    Expect.listEquals(["main", "listen"], events);
+    asyncEnd();
+  });
+}