Pass logs through transformer groups.

pkg/barback/test/logger_test.dart

Index: pkg/barback/test/logger_test.dart
diff --git a/pkg/barback/test/logger_test.dart b/pkg/barback/test/logger_test.dart
new file mode 100644
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+++ b/pkg/barback/test/logger_test.dart
@@ -0,0 +1,48 @@
+// Copyright (c) 2013, 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 barback.test.logger_test;
+
+import 'package:barback/barback.dart';
+import 'package:scheduled_test/scheduled_test.dart';
+
+import 'utils.dart';
+import 'transformer/log.dart';
+
+main() {
+  initConfig();
+
+  test("logs messages from a transformer", () {
+    var transformer = new LogTransformer([
+      "error: This is an error.",
+      "warning: This is a warning.",
+      "info: This is info."
+    ]);
+    initGraph(["app|foo.txt"], {
+      "app": [[transformer]]
+    });
+
+    updateSources(["app|foo.txt"]);
+    buildShouldLog(LogLevel.ERROR, equals("This is an error."));
+    buildShouldLog(LogLevel.WARNING, equals("This is a warning."));
+    buildShouldLog(LogLevel.INFO, equals("This is info."));
+  });
+
+  test("logs messages from a transformer group", () {
+    var transformer = new LogTransformer([
+      "error: This is an error.",
+      "warning: This is a warning.",
+      "info: This is info."
+    ]);
+
+    initGraph(["app|foo.txt"], {"app": [
+      [new TransformerGroup([[transformer]])]
+    ]});
+
+    updateSources(["app|foo.txt"]);
+    buildShouldLog(LogLevel.ERROR, equals("This is an error."));
+    buildShouldLog(LogLevel.WARNING, equals("This is a warning."));
+    buildShouldLog(LogLevel.INFO, equals("This is info."));
+  });
+}