Addressed comments from review https://codereview.chromium.org/226263007

pkg/shelf/test/response_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 shelf.response_test;
 
 import 'dart:async';
 import 'dart:convert';
 
 import 'package:shelf/shelf.dart';
@@ skipping 139 matching lines @@
     test("is null without a Last-Modified header", () {
       expect(new Response.ok("okay!").lastModified, isNull);
     });
 
     test("comes from the Last-Modified header", () {
       expect(new Response.ok("okay!", headers: {
         'last-modified': 'Sun, 06 Nov 1994 08:49:37 GMT'
       }).lastModified, equals(DateTime.parse("1994-11-06 08:49:37z")));
     });
   });
+
+  group("context", () {
+    test("are correctly populated in ok", () {
+      expect(new Response.ok("okay!", headers: {}, context: {
+          'my-param' : 42
+      }).context['my-param'], equals(42));
+    });
+
+    test("is correctly populated in forbidden", () {
+      expect(new Response.forbidden("okay!", headers: {}, context: {
+          'my-param' : 42
+      }).context['my-param'], equals(42));
+    });
+
+    test("is correctly populated in found", () {
+      expect(new Response.found("okay!", headers: {}, context: {
+          'my-param' : 42
+      }).context['my-param'], equals(42));
+    });
+
+    test("is correctly populated in internalServerError", () {
+      expect(new Response.internalServerError(headers: {}, context: {
+          'my-param' : 42
+      }).context['my-param'], equals(42));
+    });
+
+    test("is correctly populated in movedPermanently", () {
+      expect(new Response.movedPermanently("okay!", headers: {}, context: {
+          'my-param' : 42
+      }).context['my-param'], equals(42));
+    });
+
+    test("is correctly populated in notFound", () {
+      expect(new Response.notFound("okay!", headers: {}, context: {
+          'my-param' : 42
+      }).context['my-param'], equals(42));
+    });
+
+    test("is correctly populated in notModified", () {
+      expect(new Response.notModified(headers: {}, context: {
+          'my-param' : 42
+      }).context['my-param'], equals(42));
+    });
+
+    test("is correctly populated in seeOther", () {
+      expect(new Response.seeOther("other", headers: {}, context: {
+          'my-param' : 42
+      }).context['my-param'], equals(42));
+    });
+  });
 }