anchor.diff:      group('custom', () {
         test('simple', () {
           expect(HttpServer.bind('localhost', 0).then((server) {
  -          var dir = new Directory('').createTempSync();
  +          var dir = Directory.systemTemp.createTempSync('http_server_virtual_');
             var virDir = new VirtualDirectory(dir.path);
             virDir.allowDirectoryListing = true;
             virDir.setDirectoryHandler((dir2, request) {
  
positive.code: 
        test('file-not-exists', () {
          expect(HttpServer.bind('localhost', 0).then((server) {
            var dir = new Directory('').createTempSync();
            var virDir = new VirtualDirectory(dir.path);
  
            virDir.serve(server);
  
negative.code: 
        test('dirs', () {
          expect(HttpServer.bind('localhost', 0).then((server) {
            var dir = Directory.systemTemp.createTempSync('http_server_virtual_');
            var virDir = new VirtualDirectory(dir.path);
            for (int i = 0; i < 10; i++) {
              new Directory('${dir.path}/$i').createSync();
  