First stab at a dev server in pub using barback.

sdk/lib/_internal/pub/test/serve/404_on_missing_file_test.dart

Index: sdk/lib/_internal/pub/test/serve/404_on_missing_file_test.dart
diff --git a/sdk/lib/_internal/pub/test/serve/404_on_missing_file_test.dart b/sdk/lib/_internal/pub/test/serve/404_on_missing_file_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..3e3606fe85d700b971d0bc1dc056782815883864
--- /dev/null
+++ b/sdk/lib/_internal/pub/test/serve/404_on_missing_file_test.dart
@@ -0,0 +1,24 @@
+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS d.file

[nweiz, 2013/07/25 22:58:58]

2013. Same for other new test files.

[Bob Nystrom, 2013/07/26 20:20:11]

Done.

+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE d.file.

[nweiz, 2013/07/25 22:58:58]

"LICENSE file."

[Bob Nystrom, 2013/07/26 20:20:11]

Ha, done. :)

+
+library pub_tests;
+
+import 'dart:io';
+
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+import 'utils.dart';
+
+main() {
+  initConfig();
+  integration("responds with a 404 for a missing file", () {
+    d.dir(appPath, [
+      d.appPubspec()
+    ]).create();
+
+    startPubServe();
+    requestShould404("index.html");
+    endPubServe();
+  });
+}