Install barback from a hosted source in all tests.

test/serve/supports_user_defined_lazy_transformers_test.dart

Index: test/serve/supports_user_defined_lazy_transformers_test.dart
diff --git a/test/serve/supports_user_defined_lazy_transformers_test.dart b/test/serve/supports_user_defined_lazy_transformers_test.dart
index a3ec33f5d8292a85f5273c504694f8402b3c9307..de09be8fe77961f87922354dc3f85b3956a71ae0 100644
--- a/test/serve/supports_user_defined_lazy_transformers_test.dart
+++ b/test/serve/supports_user_defined_lazy_transformers_test.dart
@@ -10,10 +10,13 @@ import 'utils.dart';
 
 main() {
   integration("supports a user-defined lazy transformer", () {
+    serveBarback();
+
     d.dir(appPath, [
       d.pubspec({
         "name": "myapp",
-        "transformers": ["myapp/src/transformer"]
+        "transformers": ["myapp/src/transformer"],
+        "dependencies": {"barback": "any"}
       }),
       d.dir("lib", [d.dir("src", [
         d.file("transformer.dart", LAZY_TRANSFORMER)
@@ -23,8 +26,7 @@ main() {
       ])
     ]).create();
 
-    createLockFile('myapp', pkg: ['barback']);
-
+    pubGet();
     var server = pubServe();
     // The build should complete without the transformer logging anything.
     server.stdout.expect('Build completed successfully');