pkg/http_parser: fixed edge cases with 9s and single-digit days

pkg/http_parser/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';
 
 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);
+
+      expect(parsed, date);
+    });
+
+    test('end of year', () {
+      var date = new DateTime.utc(1999, 12, 31, 23, 59, 59);
+      var formatted = formatHttpDate(date);
+
+      expect(formatted, 'Fri, 31 Dec 1999 23:59:59 GMT');
+      var parsed = parseHttpDate(formatted);
+
+      expect(parsed, date);
+    });
+
+    test('start of year', () {
+      var date = new DateTime.utc(2000, 1, 1, 0, 0, 0);
+      var formatted = formatHttpDate(date);
+
+      expect(formatted, 'Sat, 01 Jan 2000 00:00:00 GMT');
+      var parsed = parseHttpDate(formatted);
+
+      expect(parsed, date);
+    });
+  });
+
   group("parse", () {
     group("RFC 1123", () {
       test("parses the example date", () {
         var date = parseHttpDate("Sun, 06 Nov 1994 08:49:37 GMT");
         expect(date.day, equals(6));
         expect(date.month, equals(DateTime.NOVEMBER));
         expect(date.year, equals(1994));
         expect(date.hour, equals(8));
         expect(date.minute, equals(49));
         expect(date.second, equals(37));
@@ skipping 285 matching lines @@
             throwsFormatException);
       });
 
       test("disallows trailing whitespace", () {
         expect(() => parseHttpDate("Sun November 0 08:49:37 1994 "),
             throwsFormatException);
       });
     });
   });
 }