Mock getExternalStorageDirectory on Flutter - flutter

Question

I´m trying mock the function getExternalStorageDirectory, but alway return the error:
"UnsupportedError (Unsupported operation: Functionality only available on Android)"
I´m using the method setMockMethodCallHandler to mock it, but the erro occurs before the method be called.
test method
test('empty listReportModel', () async {
TestWidgetsFlutterBinding.ensureInitialized();
final directory = await Directory.systemTemp.createTemp();
const MethodChannel channel =
MethodChannel('plugins.flutter.io/path_provider');
channel.setMockMethodCallHandler((MethodCall methodCall) async {
if (methodCall.method == 'getExternalStorageDirectory') {
return directory.path;
}
return ".";
});
when(Modular.get<IDailyGainsController>().listDailyGains())
.thenAnswer((_) => Future.value(listDailyGainsModel));
when(Modular.get<IReportsController>().listReports())
.thenAnswer((_) => Future.value(new List<ReportsModel>()));
var configurationController = Modular.get<IConfigurationController>();
var response = await configurationController.createBackup();
expect(response.filePath, null);
});
method
Future<CreateBackupResponse> createBackup() async {
CreateBackupResponse response = new CreateBackupResponse();
var dailyGains = await exportDailyGainsToCSV();
var reports = await exportReportsToCSV();
final Directory directory = await getApplicationDocumentsDirectory();
final Directory externalDirectory = await getExternalStorageDirectory();
if (dailyGains.filePath != null && reports.filePath != null) {
File dailyGainsFile = File(dailyGains.filePath);
File reportsFile = File(reports.filePath);
var encoder = ZipFileEncoder();
encoder.create(externalDirectory.path + "/" + 'backup.zip');
encoder.addFile(dailyGainsFile);
encoder.addFile(reportsFile);
encoder.close();
await _removeFile(dailyGainsFile.path);
await _removeFile(reportsFile.path);
response.filePath = directory.path + "/" + 'backup.zip';
}
return response;
}

Answer 1

As in pub.dev stated:
path_provider now uses a PlatformInterface, meaning that not all
platforms share the a single PlatformChannel-based implementation.
With that change, tests should be updated to mock PathProviderPlatform
rather than PlatformChannel.
That means somewhere in your test directory you create the following mock class:
import 'package:mockito/mockito.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:path_provider/path_provider.dart';
import 'package:path_provider_platform_interface/path_provider_platform_interface.dart';
import 'package:plugin_platform_interface/plugin_platform_interface.dart';
const String kTemporaryPath = 'temporaryPath';
const String kApplicationSupportPath = 'applicationSupportPath';
const String kDownloadsPath = 'downloadsPath';
const String kLibraryPath = 'libraryPath';
const String kApplicationDocumentsPath = 'applicationDocumentsPath';
const String kExternalCachePath = 'externalCachePath';
const String kExternalStoragePath = 'externalStoragePath';
class MockPathProviderPlatform extends Mock
with MockPlatformInterfaceMixin
implements PathProviderPlatform {
Future<String> getTemporaryPath() async {
return kTemporaryPath;
}
Future<String> getApplicationSupportPath() async {
return kApplicationSupportPath;
}
Future<String> getLibraryPath() async {
return kLibraryPath;
}
Future<String> getApplicationDocumentsPath() async {
return kApplicationDocumentsPath;
}
Future<String> getExternalStoragePath() async {
return kExternalStoragePath;
}
Future<List<String>> getExternalCachePaths() async {
return <String>[kExternalCachePath];
}
Future<List<String>> getExternalStoragePaths({
StorageDirectory type,
}) async {
return <String>[kExternalStoragePath];
}
Future<String> getDownloadsPath() async {
return kDownloadsPath;
}
}
And build your tests the following way:
void main() {
group('PathProvider', () {
TestWidgetsFlutterBinding.ensureInitialized();
setUp(() async {
PathProviderPlatform.instance = MockPathProviderPlatform();
// This is required because we manually register the Linux path provider when on the Linux platform.
// Will be removed when automatic registration of dart plugins is implemented.
// See this issue https://github.com/flutter/flutter/issues/52267 for details
disablePathProviderPlatformOverride = true;
});
test('getTemporaryDirectory', () async {
Directory result = await getTemporaryDirectory();
expect(result.path, kTemporaryPath);
});
}
}
Here you can check out the complete example.