anchor.diff:                slivers: <Widget>[
                   buildAListOfStuff(),
                   CupertinoSliverRefreshControl( // it's in the middle now.
  -                  builder: builder,
  -                  onRefresh: onRefresh,
  +                  builder: mockHelper.builder,
  +                  onRefresh: mockHelper.refreshTask,
                   ),
                   buildAListOfStuff(),
                 ],
  
positive.code:             child: CustomScrollView(
                slivers: <Widget>[
                  CupertinoSliverRefreshControl(
                    builder: builder,
                    onRefresh: onRefresh,
                  ),
                  buildAListOfStuff(),
                ],
  
negative.code:       await tester.pump();
  
        // Refresh indicator still being told to layout the same way.
        expect(mockHelper.invocations, contains(matchesBuilder(
          refreshState: RefreshIndicatorMode.refresh,
          pulledExtent: 60,
          refreshIndicatorExtent: 60, // Default value.
          refreshTriggerPullDistance: 100, // Default value.
        )));
  
        // Now the sliver is scrolled off screen.
        expect(
  