Add a validator that checks that the lib directory is not empty.

utils/tests/pub/oauth2_test.dart

 // Copyright (c) 2012, 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 oauth2_test;
 
 import 'dart:io';
 import 'dart:json';
 import 'dart:uri';
 
 import 'test_pub.dart';
 import '../../../pkg/http/lib/http.dart' as http;
 import '../../../pkg/unittest/lib/unittest.dart';
 import '../../pub/io.dart';
 import '../../pub/utils.dart';
 
 main() {
-  setUp(() {
-    dir(appPath, [
-      libPubspec("test_pkg", "1.0.0"),
-      file("LICENSE", "Eh, do what you want.")
-    ]).scheduleCreate();
-  });
+  setUp(() => normalPackage.scheduleCreate());
 
   test('with no credentials.json, authenticates and saves credentials.json',
       () {
     var server = new ScheduledServer();
     var pub = startPubLish(server);
     authorizePub(pub, server);
 
     server.handle('GET', '/packages/versions/new.json', (request, response) {
       expect(request.headers.value('authorization'),
           equals('Bearer access token'));
@@ skipping 147 matching lines @@
 
       response.headers.contentType = new ContentType("application", "json");
       response.outputStream.writeString(JSON.stringify({
         "access_token": accessToken,
         "token_type": "bearer"
       }));
       response.outputStream.close();
     });
   });
 }