Run pub tests against older versions of barback.

sdk/lib/_internal/pub/test/transformer/loads_a_transformer_defined_in_an_exported_library_test.dart

Index: sdk/lib/_internal/pub/test/transformer/loads_a_transformer_defined_in_an_exported_library_test.dart
diff --git a/sdk/lib/_internal/pub/test/transformer/loads_a_transformer_defined_in_an_exported_library_test.dart b/sdk/lib/_internal/pub/test/transformer/loads_a_transformer_defined_in_an_exported_library_test.dart
index d38baa6bea1f333ed8a54cb2c5457b0db20609ec..aab190047d9824f8649c3e6848941cf614bbe14e 100644
--- a/sdk/lib/_internal/pub/test/transformer/loads_a_transformer_defined_in_an_exported_library_test.dart
+++ b/sdk/lib/_internal/pub/test/transformer/loads_a_transformer_defined_in_an_exported_library_test.dart
@@ -10,27 +10,29 @@ import '../serve/utils.dart';
 
 main() {
   initConfig();
-  integration("loads a transformer defined in an exported library", () {
-    d.dir(appPath, [
-      d.pubspec({
-        "name": "myapp",
-        "transformers": ["myapp"]
-      }),
-      d.dir("lib", [
-        d.file("myapp.dart", "export 'src/transformer.dart';"),
-        d.dir("src", [
-          d.file("transformer.dart", REWRITE_TRANSFORMER)
+  withBarbackVersions("any", () {
+    integration("loads a transformer defined in an exported library", () {
+      d.dir(appPath, [
+        d.pubspec({
+          "name": "myapp",
+          "transformers": ["myapp"]
+        }),
+        d.dir("lib", [
+          d.file("myapp.dart", "export 'src/transformer.dart';"),
+          d.dir("src", [
+            d.file("transformer.dart", REWRITE_TRANSFORMER)
+          ])
+        ]),
+        d.dir("web", [
+          d.file("foo.txt", "foo")
         ])
-      ]),
-      d.dir("web", [
-        d.file("foo.txt", "foo")
-      ])
-    ]).create();
+      ]).create();
 
-    createLockFile('myapp', pkg: ['barback']);
+      createLockFile('myapp', pkg: ['barback']);
 
-    pubServe();
-    requestShouldSucceed("foo.out", "foo.out");
-    endPubServe();
+      pubServe();
+      requestShouldSucceed("foo.out", "foo.out");
+      endPubServe();
+    });
   });
 }