pkg/unittest: test cleanup

pkg/unittest/test/async_exception_test.dart

 // Copyright (c) 2013, 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 unittestTest;
+
+import 'dart:async';
 import 'dart:isolate';
-import 'dart:async';
+
 import 'package:unittest/unittest.dart';
 
-part 'unittest_test_utils.dart';
+part 'utils.dart';
 
 var testName = 'async exception test';
 
 var testFunction = (_) {
   test(testName, () {
     expectAsync(() {});
     _defer(() { throw "error!"; });
   });
 };
 
-var expected = buildStatusString(0, 1, 0, testName, message: 'Caught error!');
+final expected = buildStatusString(0, 1, 0, testName, message: 'Caught error!');