Look for SDK packages in "pkg" in addition to "lib".

utils/tests/pub/pub_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('pub_tests');
 
 #import('dart:io');
 
 #import('test_pub.dart');
 #import('../../../pkg/unittest/unittest.dart');
@@ skipping 75 matching lines @@
           ''');
     });
   });
   */
 }
 
 installCommand() {
   test('checks out a package from the SDK', () {
     dir(sdkPath, [
       file('revision', '1234'),
-      dir('lib', [
+      dir('pkg', [
         dir('foo', [
           file('foo.dart', 'main() => "foo";')
         ])
       ])
     ]).scheduleCreate();
 
     dir(appPath, [
       file('pubspec.yaml', 'dependencies:\n  foo:')
     ]).scheduleCreate();
 
@@ skipping 1032 matching lines @@
 
       run();
     });
   });
 }
 
 versionCommand() {
   test('displays the current version', () =>
     runPub(args: ['version'], output: VERSION_STRING));
 }