Upgrade to the new test package.

test/http_date_test.dart

 // Copyright (c) 2014, 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 http_parser.http_date_test;
 
 import 'package:http_parser/http_parser.dart';
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 
 void main() {
   group('format', () {
     test('many values with 9', () {
       var date = new DateTime.utc(2014, 9, 9, 9, 9, 9);
       var formatted = formatHttpDate(date);
 
       expect(formatted, 'Tue, 09 Sep 2014 09:09:09 GMT');
       var parsed = parseHttpDate(formatted);
 
@@ skipping 319 matching lines @@
             throwsFormatException);
       });
 
       test("disallows trailing whitespace", () {
         expect(() => parseHttpDate("Sun November 0 08:49:37 1994 "),
             throwsFormatException);
       });
     });
   });
 }