pkg/args: a bunch of test cleanup

pkg/args/test/parse_all_test.dart

 // Copyright (c) 2013, 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 parse_all_test;
 
 import 'package:unittest/unittest.dart';
 import 'package:args/args.dart';
 
-main() {
+void main() {
   group('ArgParser.parse(allowTrailingOptions: true) '
         'starting with a non-option', () {
     test('followed by flag', () {
       var parser = new ArgParser()..addFlag('flag');
       var args = ['A', '--flag'];
 
       var resultsAll = parser.parse(args, allowTrailingOptions: true);
       expect(resultsAll['flag'], isTrue);
       expect(resultsAll.rest, equals(['A']));
     });
@@ skipping 29 matching lines @@
     });
 
     test('followed by command', () {
       var parser = new ArgParser()..addCommand('com');
       var args = ['A', 'com'];
 
       expectThrows(parser, args);
     });
   });
 }
-expectThrows(ArgParser parser, List<String> args) =>
+
+void expectThrows(ArgParser parser, List<String> args) =>
   expect(() => parser.parse(args, allowTrailingOptions: true),
       throwsFormatException,
       reason: "with allowTrailingOptions: true");