Shard tests run by test.dart, so they can be distributed to multiple machines.

tools/testing/dart/test_options.dart

 // Copyright (c) 2011, 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("test_options_parser");
 
 #import("dart:io");
 #import("dart:builtin");
 #import("drt_updater.dart");
 
@@ skipping 133 matching lines @@
               'Print a summary report of the number of tests, by expectation',
               ['--report'],
               [],
               false,
               'bool'),
           new _TestOptionSpecification(
               'tasks',
               'The number of parallel tasks to run',
               ['-j', '--tasks'],
               [],
-              new Platform().numberOfProcessors(),
+          new Platform().numberOfProcessors(),

[Bill Hesse, 2012/03/23 22:33:56]

Fix this stray indentation.

+          'int'),
+          new _TestOptionSpecification(
+              'shards',
+              'The number of instances that the tests will be sharded over',
+              ['--shards'],
+              [],
+              1,
+              'int'),
+          new _TestOptionSpecification(
+              'shard',
+              'The index of this instance when running in sharded mode',

[Mads Ager (google), 2012/03/23 23:38:20]

Maybe we should add an early bailout check somewhere (just before expanding the
configurations maybe) that the value of the shard option is between 1 and the
shards options.

+              ['--shard'],
+              [],
+              1,
               'int'),
           new _TestOptionSpecification(
               'help',
               'Print list of options',
               ['-h', '--help'],
               [],
               false,
               'bool'),
           new _TestOptionSpecification(
               'verbose',
@@ skipping 378 matching lines @@
         return option;
       }
     }
     print('Unknown test option $name');
     exit(1);
   }
 
 
   List<_TestOptionSpecification> _options;
 }