如果最初在视口之外，如何测试Widget是否已渲染

如何解决如果最初在视口之外，如何测试Widget是否已渲染

我有这个自定义的Widget组件：

class CollectAssetDataButton extends StatelessWidget {
  const CollectAssetDataButton({ Key key }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return RaisedButton(
        child: Text(
      context
          .translate(I18NKeys.appointmentDetails.collectAssetsData)
          .toupperCase(),),onpressed: () {},);
  }
}

我正在尝试使用：

  final collectAssetsButtonFinder = find.byKey(WidgetKeysAppointmentDetails.collectAssetsButton);
  expect(collectAssetsButtonFinder,findsOneWidget);

根据https://github.com/flutter/flutter/issues/54651

中的建议

但是我仍然得到：

══╡ EXCEPTION CAUGHT BY FlutteR TEST FRAMEWORK ╞════════════════════════════════════════════════════
The following TestFailure object was thrown running a test:
  Expected: exactly one matching node in the widget tree
  Actual: _KeyFinder:<zero widgets with key [<'___appointment_details_collect_assets_button___'>]
(ignoring offstage widgets)>
   Which: means none were found but one was expected

谢谢！