Update README with testing and environment documentation

- Add environment configuration section with flavor commands
- Document specialization topic (Testing)
- Add testing strategy section with test structure

README.md

@@ -121,17 +121,87 @@ flutter gen-l10n
 flutter run
 ```
 
-### Running Tests
+### Environment Configuration
+
+The app supports multiple environments via flavor configuration:
 
-**Backend:**
 ```bash
-cd backend
-pytest -v
+# Development (default)
+flutter run
+flutter run -t lib/main_dev.dart
+
+# Production
+flutter run -t lib/main_prod.dart --release
+
+# With explicit environment variable
+flutter run --dart-define=ENV=prod
 ```
 
-**Frontend:**
+Configuration is managed in `lib/core/config/app_config.dart`.
+
+## Specialization Topic
+
+**Testing + Internationalization**
+
+This project focuses on two specialization areas for the HFTM Mobile Computing course:
+
+1. **Testing**: Comprehensive test coverage with unit, widget, and integration tests
+2. **Internationalization**: Full i18n support with English and German, locale-aware date formatting
+
+## Testing Strategy
+
+The project follows a multi-layered testing approach:
+
+### Unit Tests
+- **Domain Layer**: Entity validation, enum behavior
+- **Data Layer**: Model serialization/deserialization (JSON)
+- **Presentation Layer**: ViewModel business logic with mocked repositories
+
+### Widget Tests
+- Component rendering and display
+- User interactions (tap, input)
+- State changes and callbacks
+
+### Integration Tests
+- End-to-end user flows
+- Navigation between screens
+- Task creation and management lifecycle
+
+### Running Tests
+
 ```bash
+# Run all unit and widget tests
 flutter test
+
+# Run with coverage
+flutter test --coverage
+
+# Run integration tests (requires device/emulator)
+flutter test integration_test
+
+# Run specific test file
+flutter test test/features/tasks/presentation/viewmodels/daily_tasks_viewmodel_test.dart
+```
+
+### Test Structure
+
+```
+test/
+├── features/
+│   ├── auth/
+│   │   ├── data/models/          # Model serialization tests
+│   │   └── domain/entities/      # Entity tests
+│   ├── tasks/
+│   │   ├── data/models/
+│   │   ├── domain/
+│   │   └── presentation/
+│   │       ├── viewmodels/       # ViewModel unit tests
+│   │       └── widgets/          # Widget tests
+│   └── onboarding/
+└── helpers/                      # Test utilities
+
+integration_test/
+└── app_test.dart                 # End-to-end tests
 ```
 
 ## Internationalization (i18n)