Make Suite contain a single Group.

test/backend/declarer_test.dart

 // Copyright (c) 2015, 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/src/backend/declarer.dart';
 import 'package:test/src/backend/group.dart';
 import 'package:test/src/backend/invoker.dart';
 import 'package:test/src/backend/suite.dart';
 import 'package:test/src/backend/test.dart';
 import 'package:test/src/frontend/timeout.dart';
 import 'package:test/test.dart';
 
 import '../utils.dart';
 
 Suite _suite;
 
 void main() {
   setUp(() {
-    _suite = new Suite([]);
+    _suite = new Suite(new Group.root([]));
   });
 
   group(".test()", () {
     test("declares a test with a description and body", () async {
       var bodyRun = false;
       var tests = declare(() {
         test("description", () {
           bodyRun = true;
         });
       });
@@ skipping 508 matching lines @@
 /// doesn't throw any invisible exceptions.
 Future _runTest(Test test, {bool shouldFail: false}) {
   var liveTest = test.load(_suite);
 
   liveTest.onError.listen(shouldFail
       ? expectAsync((_) {})
       : (error) => registerException(error.error, error.stackTrace));
 
   return liveTest.run();
 }