Flutter proper way to test dart:ui on Android device - flutter

Question

I faced following problem:
My Android Flutter app has a serie of dart:ui calls, basically to do an application files backup. Lets just check how to test that it find the correct path of the app files. The function to test:
static Future<String> getUserPath() async {
final appDocDir = await getApplicationDocumentsDirectory();
final pathComponents = path.split(appDocDir.path);
pathComponents.removeLast();
final filepaths = path.join(path.joinAll(pathComponents), 'files', '.user');
if (!await Directory(filepaths).exists()) throw FileSystemException('User directory not found');
return filepaths;
}
Easy, it call different dart:ui functions to check where the user files are. It works now, but I want to write the test for this funcion. Basically I found two ways to test this is: using Flutter Drive tests to write integration tests, i followed this tutorial: https://flutter-website-staging.firebaseapp.com/testing/ . And using Flutter integration tests, using this guide: https://docs.flutter.dev/testing/integration-tests.
The test I wrote is next:
testWidgets('test_correct_path', (WidgetTester tester) async {
print('user folder: ' + await getUserPath());
assert('.user' == basename(await getUserPath()));
});
Using driver tests
I created the following folder on my project:
test_driver
├── backup.dart
└── backup_test.dart
On backup.dart
// This line imports the extension
import 'package:flutter_driver/driver_extension.dart';
import 'package:elRepoIo/main.dart' as app;
void main() {
// This line enables the extension
enableFlutterDriverExtension();
}
And on backup_test.dart I just added the needed functions after test main declaration:
void main() {
FlutterDriver driver;
// connect flutter driver to the app before executing the runs
setUpAll(() async {
driver = await FlutterDriver.connect();
});
// disconnect flutter driver from the app after executing the runs
tearDownAll(() async {
if (driver != null) {
driver.close();
}
});
// Tests down here
Then when I execute the tests using flutter drive --target=test_driver/backup.dart I receive a bunch of errors such flutter/packages/flutter_test/lib/src/frame_timing_summarizer.dart:5:8: Error: Not found: 'dart:ui' import 'dart:ui';
Using integration tests
Under
integration_test
├── backup_test.dart
I wrote the tests adding the following line:
void main() {
IntegrationTestWidgetsFlutterBinding.ensureInitialized(); // NEW
Then I run the test using flutter test integration_test/backup_test.dart -d $device_id where I get device_id using flutter devices.
If I debug this I found that the path is correct, but await Directory(filepaths).exists() is false.
It seem that if I run the app to create the folder and inmetially I run the tests the directory exist. Are integration tests deleting all file data? And how can I keep it?