Install barback from a hosted source in all tests.

test/serve_packages.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 serve_packages;
 
 import 'dart:async';
 import 'dart:convert';
 
 import 'package:path/path.dart' as p;
 import 'package:pub/src/io.dart';
+import 'package:pub/src/pubspec.dart';
+import 'package:pub/src/source_registry.dart';
 import 'package:pub/src/utils.dart';
 import 'package:pub_semver/pub_semver.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 import 'package:yaml/yaml.dart';
 
 import 'descriptor.dart' as d;
 import 'test_pub.dart';
 
 /// The [d.DirectoryDescriptor] describing the server layout of `/api/packages`
 /// on the test server.
@@ skipping 74 matching lines @@
     });
   }, 'initializing the package server');
 }
 
 /// Like [servePackages], but instead creates an empty server with no packages
 /// registered.
 ///
 /// This will always replace a previous server.
 void serveNoPackages() => servePackages((_) {}, replace: true);
 
+/// A shortcut for [servePackages] that serves the version of barback used by
+/// pub.
+void serveBarback() {
+  servePackages((builder) {
+    builder.serveRealPackage('barback');
+  });
+}
+
 /// A builder for specifying which packages should be served by [servePackages].
 class PackageServerBuilder {
   /// A map from package names to a list of concrete packages to serve.
   final _packages = new Map<String, List<_ServedPackage>>();
 
   /// A group of futures from [serve] calls.
   ///
   /// This should be accessed by calling [_awair].
   var _futures = new FutureGroup();
 
@@ skipping 24 matching lines @@
       if (contents == null) contents = [d.libDir(name, "$name $version")];
       contents = [d.file("pubspec.yaml", yaml(pubspecFields))]
           ..addAll(contents);
 
       var packages = _packages.putIfAbsent(name, () => []);
       packages.add(new _ServedPackage(pubspecFields, contents));
     }));
   }
 
   /// Serves the versions of [package] and all its dependencies that are
-  /// currently checked into the Dart repository.
-  void serveRepoPackage(String package) {
+  /// currently depended on by pub.
+  void serveRealPackage(String package) {
     _addPackage(name) {
       if (_packages.containsKey(name)) return;
       _packages[name] = [];
 
       var root = packagePath(name);
       var pubspec = new Map.from(loadYaml(
           readTextFile(p.join(root, 'pubspec.yaml'))));
 
       // Remove any SDK constraints since we don't have a valid SDK version
       // while testing.
@@ skipping 24 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);
 }