paperless-mobile/integration_test/test_add_document.dart

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

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

  testWidgets('screenshot', (WidgetTester tester) async {
    // Build the app.

    // This is required prior to taking the screenshot (Android only).
    await binding.convertFlutterSurfaceToImage();

    // Trigger a frame.
    await tester.pumpAndSettle();
    await binding.takeScreenshot('screenshot-1');
  });
}