Add isActive field on Timer.

tests/lib/async/timer_isActive_test.dart

+// Copyright (c) 2011, 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 '../../../pkg/unittest/lib/unittest.dart';
+
+main() {
+
+  test("timer isActive test", () {
+    Timer t;
+
+    void checkNotActive() => expect(t.isActive, equals(false));

[floitsch, 2013/07/01 12:49:43]

nit: if the function is that small, just use it at its use-site.

Timer timer;
timer = new Timer(const Duration(seconds: 1),
                  expectAsync0(() => expect(timer.isActive, equals(false)));

[zarah, 2013/07/01 16:15:35]

Done.

+
+    t = new Timer(new Duration(seconds: 1), expectAsync0(checkNotActive));
+    expect(t.isActive, equals(true));
+  });
+
+  test("periodic timer cancel test", () {
+    Timer t;
+
+    int i = 0;
+    void checkActive(Timer timer) {
+      expect(t.isActive, equals(true));
+      if (i == 2) {
+        t.cancel();
+        expect(t.isActive, equals(false));
+      }
+      i++;
+    }
+
+    t = new Timer.periodic(new Duration(milliseconds: 1),
+                           expectAsync1(checkActive, count: 3));
+  });

[floitsch, 2013/07/01 12:49:43]

check that timer is active outside callback.

[zarah, 2013/07/01 16:15:35]

Done.

+
+  test("timer cancel test", () {
+    Timer timer;
+    Timer canceller;
+
+    void unreachable() {
+      fail("Cancelled timer should not be reached");
+    }
+
+    void cancelOtherTimer() {
+      expect(timer.isActive, equals(true));
+      timer.cancel();
+      expect(timer.isActive, equals(t));

[floitsch, 2013/07/01 12:49:43]

t?

[zarah, 2013/07/01 16:15:35]

t-> true

+    }
+
+    timer = new Timer(new Duration(milliseconds: 1),

[floitsch, 2013/07/01 12:49:43]

nits:
no need to assign it if you don't use it later.

Use Timer.run if you just want to yield before doing something:
Timer.run(expectAsync0(cancelOtherTimer));

I would assign the other timer first, so that the test becomes easier to read:

Timer timer = new Timer(const Duration(seconds: 1),
                        () => fail("...");
Timer.run(expectAsync0(() {
  expect(timer.isActive, equals(true));
  timer.cancel();
  expect(timer.isActive, equals(false));
});

[zarah, 2013/07/01 16:15:35]

Done.

+                          expectAsync0(cancelOtherTimer));
+    timer = new Timer(new Duration(milliseconds: 1000),

[floitsch, 2013/07/01 12:49:43]

seconds: 1

[zarah, 2013/07/01 16:15:35]

Done.

+                  expectAsync0(unreachable, count: 0));

[floitsch, 2013/07/01 12:49:43]

this line should not be reached. -> don't expectAsync0 it.

[zarah, 2013/07/01 16:15:35]

Done.

+  });
+}