Flutter integration test screenshots (including Windows)

app_test.dart

import 'dart:io' as io;

import 'package:flutter_test/flutter_test.dart';
import 'package:integration_test/integration_test.dart';

import 'src/util/screenshot.dart';

void main() {
  final binding = IntegrationTestWidgetsFlutterBinding.ensureInitialized();

  group('End-to-end_tests', () {
    setUp(() async {
      //await $initializeApp();
    });

    tearDown(() async {
      //await $disposeApp();
    });

    testWidgets('App', (tester) async {
      // Prepare for screenshot.
      final shot = screenshot(tester);
      io.Directory('integration_test/screenshots').createSync(recursive: true);

      // Build our app and trigger a frame.
      await tester.pumpWidget(const App());
      
      // ...

      final appScreenshot = await shot();
      io.File('integration_test/screenshots/app.png').writeAsBytesSync(appScreenshot);
    });
  });
}

screenshot.dart

import 'dart:io' as io;
import 'dart:typed_data' as td;
import 'dart:ui' as ui;

import 'package:flutter/rendering.dart' show RenderRepaintBoundary;
import 'package:flutter/widgets.dart' show WidgetsApp;
import 'package:flutter_test/flutter_test.dart';
import 'package:integration_test/integration_test.dart';

/// The [_$pixelRatio] describes the scale between the logical pixels and the
/// size of the output image. It is independent of the
/// [dart:ui.FlutterView.devicePixelRatio] for the device, so specifying 1.0
/// (the default) will give you a 1:1 mapping between logical pixels and the
/// output pixels in the image.
const double _$pixelRatio = 1.0;

/// Returns a function that takes a screenshot of the current state of the app.
Future<List<int>> Function([String? name]) screenshot(
  WidgetTester tester, [
  IntegrationTestWidgetsFlutterBinding? binding,
]) =>
    ([String? name]) async {
      await tester.pump();
      if (binding != null && name != null && (io.Platform.isAndroid || io.Platform.isIOS)) {
        if (io.Platform.isAndroid) await binding.convertFlutterSurfaceToImage();
        return await binding.takeScreenshot(name);
      } else {
        final element = tester.firstElement(find.byType(WidgetsApp));
        RenderRepaintBoundary? boundary;
        element.visitAncestorElements((element) {
          final renderObject = element.renderObject;
          if (renderObject is RenderRepaintBoundary) boundary = renderObject;
          return true;
        });
        if (boundary == null) throw StateError('No RenderRepaintBoundary found');
        final image = await boundary!.toImage(pixelRatio: _$pixelRatio);
        final bytes = await image.toByteData(format: ui.ImageByteFormat.png);
        if (bytes is! td.ByteData) throw StateError('Error converting image to bytes');
        return bytes.buffer.asUint8List();
      }
    };