Install barback from a hosted source in all tests.

test/transformer/exclusion/exclude_asset_string_test.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS d.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 pub_tests;
 
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 import '../../serve/utils.dart';
 
 main() {
   integration("allows a single string as the asset to exclude", () {
+    serveBarback();
+
     d.dir(appPath, [
       d.pubspec({
         "name": "myapp",
         "transformers": [
           {
             "myapp/src/transformer": {
               "\$exclude": "web/foo.txt"
             }
           }
-        ]
+        ],
+        "dependencies": {"barback": "any"}
       }),
       d.dir("lib", [d.dir("src", [
         d.file("transformer.dart", REWRITE_TRANSFORMER)
       ])]),
       d.dir("web", [
         d.file("foo.txt", "foo"),
         d.file("bar.txt", "bar"),
         d.dir("sub", [
           d.file("foo.txt", "foo"),
         ])
       ])
     ]).create();
 
-    createLockFile('myapp', pkg: ['barback']);
-
+    pubGet();
     pubServe();
     requestShould404("foo.out");
     requestShouldSucceed("sub/foo.out", "foo.out");
     requestShouldSucceed("bar.out", "bar.out");
     endPubServe();
   });
 }