pkg/unittest: Run each test in a Zone

tests/lib/async/future_timeout_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.
 
 library future_timeout_test;
 
 import 'dart:async';
 import '../../../pkg/unittest/lib/unittest.dart';
 
 main() {
@@ skipping 124 matching lines @@
         const Duration(milliseconds: 5), onTimeout: () {
       result.completeError("EXN6");
       return result.future;
     });
     timedOut.catchError(expectAsync2((e, s) {
       expect(e, "EXN6");
     }));
   });
 
   test("timeoutZone", () {
+    var initialZone = Zone.current;
     Zone forked;
     int registerCallDelta = 0;
     bool callbackCalled = false;
     Function callback = () {
       expect(callbackCalled, false);
       callbackCalled = true;
       expect(Zone.current, forked);
       return 42;
     };
     forked = Zone.current.fork(specification: new ZoneSpecification(
         registerCallback: (Zone self, ZoneDelegate parent, Zone origin, f()) {
           if (!identical(f, callback)) return f;
           registerCallDelta++;  // Increment calls to register.
           expect(origin, forked);
           expect(self, forked);
           return expectAsync0(() { registerCallDelta--; return f(); });
         }
     ));
     Completer completer = new Completer();
     Future timedOut;
     forked.run(() {
       timedOut = completer.future.timeout(const Duration(milliseconds: 5),
                                           onTimeout: callback);
     });
     timedOut.then(expectAsync1((v) {
       expect(callbackCalled, true);
       expect(registerCallDelta, 0);
-      expect(Zone.current, Zone.ROOT);
+      expect(Zone.current, initialZone);
       expect(v, 42);
     }));
   });
 
   test("timeoutNoFunction", () {
     Completer completer = new Completer();
     Future timedOut = completer.future.timeout(
         const Duration(milliseconds: 5));
     timedOut.catchError(expectAsync2((e, s) {
       expect(e, new isInstanceOf<TimeoutException>());
       expect(e.duration, const Duration(milliseconds: 5));
       expect(s, null);
     }));
   });
 }