anchor.diff:            itemBuilder: (context, index) {
               assert(index >= 0 && index <= itemCount - 1);
               return SizedBox(
  -              height: itemHeight,
  +              height:
  +                  variableHeight ? (itemHeight + (index % 13) * 5) : itemHeight,
                 child: Text('Item $index'),
               );
             },
  
positive.code:             .itemLeadingEdge,
          0.5);
    });
  
    testWidgets('Scroll to 100 and position at bottom',
        (WidgetTester tester) async {
  
negative.code:     bool addRepaintBoundaries = true,
      bool addAutomaticKeepAlives = true,
      double minCacheExtent,
      bool variableHeight = false,
    }) async {
      tester.binding.window.devicePixelRatioTestValue = 1.0;
      tester.binding.window.physicalSizeTestValue =
  