Refactor version_solver_test.

test/package_server.dart

 // Copyright (c) 2016, 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 'dart:convert';
 
 import 'package:path/path.dart' as p;
 import 'package:pub/src/io.dart';
 import 'package:pub/src/utils.dart';
@@ skipping 56 matching lines @@
 
   /// The current [PackageServerBuilder] that a user uses to specify which
   /// package to serve.
   ///
   /// This is preserved so that additional packages can be added.
   var _builder = new PackageServerBuilder._();
 
   /// A future that will complete to the port used for the server.
   Future<int> get port => _inner.port;
 
+  /// A future that will complete to the URL for the server.
+  Future<String> get url async => 'http://localhost:${await port}';
+
   /// Creates an HTTP server that replicates the structure of pub.dartlang.org.
   ///
   /// Calls [callback] with a [PackageServerBuilder] that's used to specify
   /// which packages to serve.
   PackageServer(void callback(PackageServerBuilder builder)) {
     _inner = new DescriptorServer([
       d.dir('api', [_servedApiPackageDir]),
       _servedPackageDir
     ]);
 
@@ skipping 130 matching lines @@
 
 /// A package that's intended to be served.
 class _ServedPackage {
   final Map pubspec;
   final List<d.Descriptor> contents;
 
   Version get version => new Version.parse(pubspec['version']);
 
   _ServedPackage(this.pubspec, this.contents);
 }