Add a --pause-after-load flag for debugging.

lib/src/runner/configuration.dart

 // Copyright (c) 2015, 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.runner.configuration;
 
 import 'dart:io';
 import 'dart:math' as math;
 
 import 'package:args/args.dart';
@@ skipping 38 matching lines @@
         allowMultiple: true);
     parser.addOption("concurrency",
         abbr: 'j',
         help: 'The number of concurrent test suites run.\n'
             '(defaults to $_defaultConcurrency)',
         valueHelp: 'threads');
     parser.addOption("pub-serve",
         help: 'The port of a pub serve instance serving "test/".',
         hide: !supportsPubServe,
         valueHelp: 'port');
+    parser.addFlag("pause-after-load",
+        help: 'Pauses for debugging before any tests execute.\n'
+            'Implies --concurrency=1.\n'
+            'Currently only supported for browser tests.',
+        negatable: false);
     parser.addOption("reporter",
         abbr: 'r',
         help: 'The runner used to print test results.',
         allowed: ['compact', 'expanded'],
         defaultsTo: Platform.isWindows ? 'expanded' : 'compact',
         allowedHelp: {
       'compact': 'A single line, updated continuously.',
       'expanded': 'A separate line for each update.'
     });
     parser.addFlag("verbose-trace", negatable: false,
@@ skipping 19 matching lines @@
   bool get version => _options['version'];
 
   /// Whether stack traces should be presented as-is or folded to remove
   /// irrelevant packages.
   bool get verboseTrace => _options['verbose-trace'];
 
   /// Whether JavaScript stack traces should be left as-is or converted to
   /// Dart-like traces.
   bool get jsTrace => _options['js-trace'];
 
+  /// Whether to pause for debugging after loading each test suite.
+  bool get pauseAfterLoad => _options['pause-after-load'];
+
   /// The package root for resolving "package:" URLs.
   String get packageRoot => _options['package-root'] == null
       ? p.join(p.current, 'packages')
       : _options['package-root'];
 
   /// The name of the reporter to use to display results.
   String get reporter => _options['reporter'];
 
   /// The URL for the `pub serve` instance from which to load tests, or `null`
   /// if tests should be loaded from the filesystem.
@@ skipping 51 matching lines @@
   /// [FormatException] it throws with additional information.
   _wrapFormatException(String name, parse(value)) {
     try {
       return parse(_options[name]);
     } on FormatException catch (error) {
       throw new FormatException('Couldn\'t parse --$name "${_options[name]}": '
           '${error.message}');
     }
   }
 }