flutter-go/packages/flutter_web/test/widgets/syncing_test.dart

// Copyright 2015 The Chromium 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_web_test/flutter_web_test.dart';
import 'package:flutter_web/widgets.dart';

class TestWidget extends StatefulWidget {
  const TestWidget({this.child, this.persistentState, this.syncedState});

  final Widget child;
  final int persistentState;
  final int syncedState;

  @override
  TestWidgetState createState() => TestWidgetState();
}

class TestWidgetState extends State<TestWidget> {
  int persistentState;
  int syncedState;
  int updates = 0;

  @override
  void initState() {
    super.initState();
    persistentState = widget.persistentState;
    syncedState = widget.syncedState;
  }

  @override
  void didUpdateWidget(TestWidget oldWidget) {
    super.didUpdateWidget(oldWidget);
    syncedState = widget.syncedState;
    // we explicitly do NOT sync the persistentState from the new instance
    // because we're using that to track whether we got recreated
    updates += 1;
  }

  @override
  Widget build(BuildContext context) => widget.child;
}

void main() {
  testWidgets('no change', (WidgetTester tester) async {
    await tester.pumpWidget(Container(
        child: Container(
            child: TestWidget(persistentState: 1, child: Container()))));

    final TestWidgetState state = tester.state(find.byType(TestWidget));

    expect(state.persistentState, equals(1));
    expect(state.updates, equals(0));

    await tester.pumpWidget(Container(
        child: Container(
            child: TestWidget(persistentState: 2, child: Container()))));

    expect(state.persistentState, equals(1));
    expect(state.updates, equals(1));

    await tester.pumpWidget(Container());
  });

  testWidgets('remove one', (WidgetTester tester) async {
    await tester.pumpWidget(Container(
        child: Container(
            child: TestWidget(persistentState: 10, child: Container()))));

    TestWidgetState state = tester.state(find.byType(TestWidget));

    expect(state.persistentState, equals(10));
    expect(state.updates, equals(0));

    await tester.pumpWidget(
        Container(child: TestWidget(persistentState: 11, child: Container())));

    state = tester.state(find.byType(TestWidget));

    expect(state.persistentState, equals(11));
    expect(state.updates, equals(0));

    await tester.pumpWidget(Container());
  });

  testWidgets('swap instances around', (WidgetTester tester) async {
    const Widget a = TestWidget(
        persistentState: 0x61,
        syncedState: 0x41,
        child: Text('apple', textDirection: TextDirection.ltr));
    const Widget b = TestWidget(
        persistentState: 0x62,
        syncedState: 0x42,
        child: Text('banana', textDirection: TextDirection.ltr));
    await tester.pumpWidget(Column());

    final GlobalKey keyA = GlobalKey();
    final GlobalKey keyB = GlobalKey();

    await tester.pumpWidget(Column(children: <Widget>[
      Container(key: keyA, child: a),
      Container(key: keyB, child: b)
    ]));

    TestWidgetState first, second;

    first = tester.state(find.byWidget(a));
    second = tester.state(find.byWidget(b));

    expect(first.widget, equals(a));
    expect(first.persistentState, equals(0x61));
    expect(first.syncedState, equals(0x41));
    expect(second.widget, equals(b));
    expect(second.persistentState, equals(0x62));
    expect(second.syncedState, equals(0x42));

    await tester.pumpWidget(Column(children: <Widget>[
      Container(key: keyA, child: a),
      Container(key: keyB, child: b)
    ]));

    first = tester.state(find.byWidget(a));
    second = tester.state(find.byWidget(b));

    // same as before
    expect(first.widget, equals(a));
    expect(first.persistentState, equals(0x61));
    expect(first.syncedState, equals(0x41));
    expect(second.widget, equals(b));
    expect(second.persistentState, equals(0x62));
    expect(second.syncedState, equals(0x42));

    // now we swap the nodes over
    // since they are both "old" nodes, they shouldn't sync with each other even though they look alike

    await tester.pumpWidget(Column(children: <Widget>[
      Container(key: keyA, child: b),
      Container(key: keyB, child: a)
    ]));

    first = tester.state(find.byWidget(b));
    second = tester.state(find.byWidget(a));

    expect(first.widget, equals(b));
    expect(first.persistentState, equals(0x61));
    expect(first.syncedState, equals(0x42));
    expect(second.widget, equals(a));
    expect(second.persistentState, equals(0x62));
    expect(second.syncedState, equals(0x41));
  });
}