Install barback from a hosted source in all tests.

test/transformer/loads_a_lazy_aggregate_transformer_test.dart

Index: test/transformer/loads_a_lazy_aggregate_transformer_test.dart
diff --git a/test/transformer/loads_a_lazy_aggregate_transformer_test.dart b/test/transformer/loads_a_lazy_aggregate_transformer_test.dart
index 96b87a6c583311c5c263393c269097dcf66c2fc3..a93c9587e8b67e532890345d3ea1f212f22267f9 100644
--- a/test/transformer/loads_a_lazy_aggregate_transformer_test.dart
+++ b/test/transformer/loads_a_lazy_aggregate_transformer_test.dart
@@ -43,10 +43,13 @@ class ManyToOneTransformer extends AggregateTransformer
 
 main() {
   integration("loads a lazy aggregate transformer", () {
+    serveBarback();
+
     d.dir(appPath, [
       d.pubspec({
         "name": "myapp",
-        "transformers": ["myapp"]
+        "transformers": ["myapp"],
+        "dependencies": {"barback": "any"}
       }),
       d.dir("lib", [
         d.file("transformer.dart", AGGREGATE_TRANSFORMER),
@@ -57,8 +60,7 @@ main() {
       ])
     ]).create();
 
-    createLockFile('myapp', pkg: ['barback']);
-
+    pubGet();
     var server = pubServe();
     // The transformer should preserve laziness.
     server.stdout.expect("Build completed successfully");