Images are not visible during flutter_driver tests - flutter

Question

When running UI tests with flutter driver the assets are not displayed on iPhone simulator. They are displayed when app is run in debug mode from VS Code.
I tried to reproduce it on the example project generated by flutter create -i swift -a kotlin --androidx --org com.example example but without success. I followed exactly the same process of introducing flutter_driver tests in both apps according to this article. Unfortunately, in my app the images are not shown, and in example app they appear just fine. I compared project.pbxproj and pubspec.yaml files and they look fine to me.
For instance my pubspec.yaml:
dev_dependencies:
flutter_driver:
sdk: flutter
test: any
flutter_test:
sdk: flutter
screenshots:
flutter:
uses-material-design: true
assets:
- assets/lang/pl.json
- assets/images/
Is there anything that can help me with this issue? What can I do to debug the problem?
Logs
Beware, this is a very long log output.
flutter drive --target=test_driver/app.dart --verbose
https://gist.github.com/orestesgaolin/861c4f191773ca152b400d97ced2daeb
Flutter doctor
flutter doctor -v
[✓] Flutter (Channel stable, v1.7.8+hotfix.4, on Mac OS X 10.14.6 18G87, locale pl-PL)
• Flutter version 1.7.8+hotfix.4 at /Users/dominik/Library/flutter
• Framework revision 20e59316b8 (6 weeks ago), 2019-07-18 20:04:33 -0700
• Engine revision fee001c93f
• Dart version 2.4.0
[✓] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
• Android SDK at /Users/dominik/Library/Android/sdk
• Android NDK location not configured (optional; useful for native profiling support)
• Platform android-28, build-tools 28.0.3
• ANDROID_SDK_ROOT = /Users/dominik/Library/Android/sdk
• Java binary at: /Users/dominik/Library/Application Support/JetBrains/Toolbox/apps/AndroidStudio/ch-0/191.5791312/Android
Studio.app/Contents/jre/jdk/Contents/Home/bin/java
• Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)
• All Android licenses accepted.
[✓] Xcode - develop for iOS and macOS (Xcode 10.3)
• Xcode at /Applications/Xcode.app/Contents/Developer
• Xcode 10.3, Build version 10G8
• CocoaPods version 1.7.5
[✓] iOS tools - develop for iOS devices
• ios-deploy 1.9.4
[✓] Android Studio (version 3.5)
• Android Studio at /Users/dominik/Library/Application Support/JetBrains/Toolbox/apps/AndroidStudio/ch-0/191.5791312/Android Studio.app/Contents
• Flutter plugin version 37.1.1
• Dart plugin version 183.6270
• Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)
[✓] VS Code (version 1.37.1)
• VS Code at /Applications/Visual Studio Code.app/Contents
• Flutter extension version 3.3.0
[✓] Connected device (1 available)
• iPhone Xs Max • C1A5534A-AE3A-4FB3-95F6-993E351FF2D3 • ios • com.apple.CoreSimulator.SimRuntime.iOS-12-4 (simulator)
• No issues found!

Answer 1

So the solution was to create separate main_test.dart file that wraps whole app in DefaultAssetBundle like so:
runApp(DefaultAssetBundle(
bundle: TestAssetBundle(),
child: App(),
));
and TestAssetBundle is like so:
class TestAssetBundle extends CachingAssetBundle {
#override
Future<String> loadString(String key, {bool cache = true}) async {
final ByteData data = await load(key);
if (data == null) throw FlutterError('Unable to load asset');
return utf8.decode(data.buffer.asUint8List());
}
#override
Future<ByteData> load(String key) async => rootBundle.load(key);
}
And in app.dart you have to reference correct file:
import 'package:flutter_driver/driver_extension.dart';
import 'package:playoo_league_player/main_test.dart' as app;
void main() {
// This line enables the extension.
enableFlutterDriverExtension();
// Call the `main()` function of the app, or call `runApp` with
// any widget you are interested in testing.
app.main();
}
Full explanation can be found here: https://medium.com/#sardox.vl/flutter-test-and-randomly-missing-assets-in-goldens-ea959cdd336a

Answer 2

Those Images are not loading because of cache issues .For that we can
use
PRE CACHE IMAGES to preload the images
class App extends StatefulWidget {
#override
State<App> createState() => _AppState();
}
class _AppState extends State<App>{
late image image1
late image image2
#override
void initState() {
super.initState();
image1 = Image.asset('assets/images/');
image2 = Image.asset('assets/images/');
}
#override
void didChangeDependencies() {
pre cacheImage(image1.image, context);
pre cacheImage(image2.image, context);
super.didChangeDependencies();
}
#override
Widget build(BuildContext context) {
return Container
}
if it is multiple assets or images you can save this method as class and
initialise it from main.dart .