anchor.diff:  }
   
   Iterable _columnSpecs = [
  -
     new ChartColumnSpec(
       label: 'Time',
       type: ChartColumnSpec.TYPE_TIMESTAMP
  -    // formatter: (num val) => val.toString() + ' sdf'
     ),
     new ChartColumnSpec(
       label: 'flutter analyze flutter-repo',
  
positive.code:     DivElement areaHost = wrapper.querySelector('.chart-host');
      DivElement legendHost = wrapper.querySelector('.chart-legend-host');
  
      data ??= _placeholderData;
  
      ChartData chartData = new ChartData(_columnSpecs, data);
      ChartSeries series = new ChartSeries("Flutter Analysis Times", [1, 2], new LineChartRenderer());
  
negative.code:   )
  ];
  
  Iterable _getPlaceholderData() {
    DateTime now = new DateTime.now();
  
    return [
      [now.subtract(new Duration(days: 30)).millisecondsSinceEpoch, 0.0, 0.0],
      [now.millisecondsSinceEpoch, 0.0, 0.0],
    ];
  }
  