SliverAppBar在小部件测试中不浮动

import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {
  testWidgets('Test SliverAppBar floating behavior', (WidgetTester tester) async {
    await tester.pumpWidget(
      MaterialApp(
        home: Scaffold(
          body: CustomScrollView(
            slivers: <Widget>[
              SliverAppBar(
                floating: true,
                title: Text('My App Bar'),
              ),
              SliverList(
                delegate: SliverChildBuilderDelegate(
                  (BuildContext context, int index) {
                    return ListTile(
                      title: Text('Item $index'),
                    );
                  },
                  childCount: 20,
                ),
              ),
            ],
          ),
        ),
      ),
    );

    // Scroll the list to make the SliverAppBar float
    await tester.ensureVisible(find.text('Item 19'));

    // Verify that the SliverAppBar is floating
    expect(find.text('My App Bar'), findsOneWidget);
    expect(tester.widget<SliverAppBar>(find.byType(SliverAppBar)).pinned, isFalse);
  });
}