packages/flutter/test/widgets/pageable_list_test.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

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

Size pageSize = const Size(600.0, 300.0);
const List<int> defaultPages = <int>[0, 1, 2, 3, 4, 5];
final List<GlobalKey> globalKeys = defaultPages.map<GlobalKey>((_) => GlobalKey()).toList();
int? currentPage;

Widget buildPage(int page) {
  return SizedBox(
    key: globalKeys[page],
    width: pageSize.width,
    height: pageSize.height,
    child: Text(page.toString()),
  );
}

Widget buildFrame({
  bool reverse = false,
  List<int> pages = defaultPages,
  required TextDirection textDirection,
}) {
  final PageView child = PageView(
    reverse: reverse,
    onPageChanged: (int page) { currentPage = page; },
    children: pages.map<Widget>(buildPage).toList(),
  );

  // The test framework forces the frame to be 800x600, so we need to create
  // an outer container where we can change the size.
  return Directionality(
    textDirection: textDirection,
    child: Center(
      child: SizedBox(
        width: pageSize.width, height: pageSize.height, child: child,
      ),
    ),
  );
}

Future<void> page(WidgetTester tester, Offset offset) {
  return TestAsyncUtils.guard(() async {
    final String itemText = currentPage != null ? currentPage.toString() : '0';
    await tester.drag(find.text(itemText), offset);
    await tester.pumpAndSettle();
  });
}

Future<void> pageLeft(WidgetTester tester) {
  return page(tester, Offset(-pageSize.width, 0.0));
}

Future<void> pageRight(WidgetTester tester) {
  return page(tester, Offset(pageSize.width, 0.0));
}

void main() {
  testWidgets('PageView default control', (WidgetTester tester) async {
    await tester.pumpWidget(
      Directionality(
        textDirection: TextDirection.ltr,
        child: Center(
          child: PageView(),
        ),
      ),
    );
  });

  testWidgets('PageView control test (LTR)', (WidgetTester tester) async {
    currentPage = null;
    await tester.pumpWidget(buildFrame(textDirection: TextDirection.ltr));
    expect(currentPage, isNull);
    await pageLeft(tester);
    expect(currentPage, equals(1));

    expect(find.text('0'), findsNothing);
    expect(find.text('1'), findsOneWidget);
    expect(find.text('2'), findsNothing);
    expect(find.text('3'), findsNothing);
    expect(find.text('4'), findsNothing);
    expect(find.text('5'), findsNothing);

    await pageRight(tester);
    expect(currentPage, equals(0));

    expect(find.text('0'), findsOneWidget);
    expect(find.text('1'), findsNothing);
    expect(find.text('2'), findsNothing);
    expect(find.text('3'), findsNothing);
    expect(find.text('4'), findsNothing);
    expect(find.text('5'), findsNothing);

    await pageRight(tester);
    expect(currentPage, equals(0));
  });

  testWidgets('PageView with reverse (LTR)', (WidgetTester tester) async {
    currentPage = null;
    await tester.pumpWidget(buildFrame(reverse: true, textDirection: TextDirection.ltr));
    await pageRight(tester);
    expect(currentPage, equals(1));

    expect(find.text('0'), findsNothing);
    expect(find.text('1'), findsOneWidget);
    expect(find.text('2'), findsNothing);
    expect(find.text('3'), findsNothing);
    expect(find.text('4'), findsNothing);
    expect(find.text('5'), findsNothing);

    await pageLeft(tester);
    expect(currentPage, equals(0));

    expect(find.text('0'), findsOneWidget);
    expect(find.text('1'), findsNothing);
    expect(find.text('2'), findsNothing);
    expect(find.text('3'), findsNothing);
    expect(find.text('4'), findsNothing);
    expect(find.text('5'), findsNothing);

    await pageLeft(tester);
    expect(currentPage, equals(0));

    expect(find.text('0'), findsOneWidget);
    expect(find.text('1'), findsNothing);
    expect(find.text('2'), findsNothing);
    expect(find.text('3'), findsNothing);
    expect(find.text('4'), findsNothing);
    expect(find.text('5'), findsNothing);
  });

  testWidgets('PageView control test (RTL)', (WidgetTester tester) async {
    currentPage = null;
    await tester.pumpWidget(buildFrame(textDirection: TextDirection.rtl));
    await pageRight(tester);
    expect(currentPage, equals(1));

    expect(find.text('0'), findsNothing);
    expect(find.text('1'), findsOneWidget);
    expect(find.text('2'), findsNothing);
    expect(find.text('3'), findsNothing);
    expect(find.text('4'), findsNothing);
    expect(find.text('5'), findsNothing);

    await pageLeft(tester);
    expect(currentPage, equals(0));

    expect(find.text('0'), findsOneWidget);
    expect(find.text('1'), findsNothing);
    expect(find.text('2'), findsNothing);
    expect(find.text('3'), findsNothing);
    expect(find.text('4'), findsNothing);
    expect(find.text('5'), findsNothing);

    await pageLeft(tester);
    expect(currentPage, equals(0));

    expect(find.text('0'), findsOneWidget);
    expect(find.text('1'), findsNothing);
    expect(find.text('2'), findsNothing);
    expect(find.text('3'), findsNothing);
    expect(find.text('4'), findsNothing);
    expect(find.text('5'), findsNothing);
  });

  testWidgets('PageView with reverse (RTL)', (WidgetTester tester) async {
    currentPage = null;
    await tester.pumpWidget(buildFrame(reverse: true, textDirection: TextDirection.rtl));
    expect(currentPage, isNull);
    await pageLeft(tester);
    expect(currentPage, equals(1));

    expect(find.text('0'), findsNothing);
    expect(find.text('1'), findsOneWidget);
    expect(find.text('2'), findsNothing);
    expect(find.text('3'), findsNothing);
    expect(find.text('4'), findsNothing);
    expect(find.text('5'), findsNothing);

    await pageRight(tester);
    expect(currentPage, equals(0));

    expect(find.text('0'), findsOneWidget);
    expect(find.text('1'), findsNothing);
    expect(find.text('2'), findsNothing);
    expect(find.text('3'), findsNothing);
    expect(find.text('4'), findsNothing);
    expect(find.text('5'), findsNothing);

    await pageRight(tester);
    expect(currentPage, equals(0));
  });
}