anchor.diff:          child: new Column(
             children: <Widget>[
               new Test1215DismissableWidget('1'),
  -            new Test1215DismissableWidget('2')
  -          ]
  -        )
  -      )
  +            new Test1215DismissableWidget('2'),
  +          ],
  +        ),
  +      ),
       ));
       expect(find.text('1'), findsOneWidget);
       expect(find.text('2'), findsOneWidget);
  
positive.code:       key: new ObjectKey(text),
        child: new AspectRatio(
          aspectRatio: 1.0,
          child: new Text(this.text)
        )
      );
    }
  }
  
negative.code: Widget buildTest({ double startToEndThreshold }) {
    Widget buildDismissableItem(int item) {
      return new Dismissable(
        key: new ValueKey<int>(item),
        direction: dismissDirection,
        onDismissed: (DismissDirection direction) {
          handleOnDismissed(direction, item);
        },
        onResize: () {
          handleOnResize(item);
        },
        background: background,
        dismissThresholds: startToEndThreshold == null
            ? <DismissDirection, double>{}
            : <DismissDirection, double>{DismissDirection.startToEnd: startToEndThreshold},
        child: new Container(
          width: itemExtent,
          height: itemExtent,
          child: new Text(item.toString())
        ),
      );
    }
  
    return new Container(
        padding: const EdgeInsets.all(10.0),
        child: new ScrollableList(
          scrollDirection: scrollDirection,
          itemExtent: itemExtent,
          children: <int>[0, 1, 2, 3, 4]
            .where((int i) => !dismissedItems.contains(i))
            .map(buildDismissableItem),
        )
    );
  }
  