Exit with an error on unexpected command line arguments.

sdk/lib/_internal/pub/test/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 'package:scheduled_test/scheduled_test.dart';
 
 import 'descriptor.dart' as d;
 import 'test_pub.dart';
@@ skipping 96 matching lines @@
     // TODO(rnystrom): When pub has command-specific options, a more precise
     // error message would be good here.
     schedulePub(args: ['version', '--blorf'],
         error: '''
         Could not find an option named "blorf".
         Run "pub help" to see available options.
         ''',
         exitCode: 64);
   });
 
+  integration('an unexpected argument displays an error message', () {
+    schedulePub(args: ['version', 'unexpected'],
+        output: '''
+        Print pub version.
+
+        Usage: pub version
+         -h, --help    Print usage information for this command.
+        ''',
+        error: '''
+        Command does not take any arguments.
+        ''',
+        exitCode: 64);
+  });
+
   group('help', () {
     integration('shows help for a command', () {
       schedulePub(args: ['help', 'get'],
           output: '''
             Get the current package's dependencies.
 
             Usage: pub get
             -h, --help            Print usage information for this command.
                 --[no-]offline    Use cached packages instead of accessing the network.
             ''');
@@ skipping 41 matching lines @@
       // The "version" file generated on developer builds is a little funky and
       // we need to make sure we don't choke on it.
       d.dir(sdkPath, [
         d.file('version', '0.1.2.0_r16279_bobross'),
       ]).create();
 
       schedulePub(args: ['version'], output: "Pub 0.1.2+0.r16279.bobross\n");
     });
   });
 }