anchor.diff:  }
   
   abstract class WebDriverBrowser extends Browser {
  -  static int _nextPort = 4444;
  -  final int _port = _nextPort++;
     WebDriver _driver;
   
     String get driverExecutable;
  
positive.code:     return true;
    }
  
    Future<void> _createDriver() async {
      for (var i = 5; i >= 0; i--) {
        // Give the driver process some time to be ready to accept connections.
        await Future.delayed(const Duration(seconds: 1));
        try {
          _driver = await createDriver(
              uri: Uri.parse('http://localhost:$_port/'),
              desired: desiredCapabilities);
        } catch (error) {
          if (i > 0) {
  
negative.code:   @override
    Future<bool> start(String url) async {
      _logEvent('Starting $this browser on: $url');
      var port = await _findUnusedPort();
      if (!await startBrowserProcess(
          driverExecutable, ['--port', '$port', ...driverArguments])) {
        return false;
      }
      await _createDriver(port);
      await _driver.get(url);
      try {
        _logEvent('Got version: ${await version}');
  