pkg/args: a bunch of test cleanup

pkg/args/test/command_test.dart

Index: pkg/args/test/command_test.dart
diff --git a/pkg/args/test/command_test.dart b/pkg/args/test/command_test.dart
index 6115ab1c2d323bd935f5c5d5b9944346cd3ae87d..1380e160087914b36198eb1a5cbdef90caea531b 100644
--- a/pkg/args/test/command_test.dart
+++ b/pkg/args/test/command_test.dart
@@ -6,8 +6,9 @@ library command_test;
 
 import 'package:unittest/unittest.dart';
 import 'package:args/args.dart';
+import 'utils.dart';
 
-main() {
+void main() {
   group('ArgParser.addCommand()', () {
     test('creates a new ArgParser if none is given', () {
       var parser = new ArgParser();
@@ -204,11 +205,3 @@ main() {
     });
   });
 }
-
-throwsIllegalArg(function) {
-  expect(function, throwsArgumentError);
-}
-
-throwsFormat(ArgParser parser, List<String> args) {
-  expect(() => parser.parse(args), throwsFormatException);
-}