flutter-testing（Flutter 测试）

Testing Strategy

• Test Pyramid: More unit and widget tests, fewer integration tests. Unit tests are fastest and cheapest.
• Mirror Test Rule: 100% logic and widget coverage. No code without a test.
• Mirror Organization: Test files MUST strictly mirror the lib/ directory structure and end with _test.dart.
• Coverage Targets: Target 100% logic coverage for domain and bloc layers.
• Test Independence: Each test MUST be independent. No shared mutable state between tests.

Unit Testing

• Follow the Arrange-Act-Assert (Given-When-Then) convention for clear and maintainable tests
• Use mocks for dependencies except for lightweight third-party services
• Test business logic in isolation from the UI
• For tests, ensure to create 5 to 8 tests for logical operations with real scenarios
• Mocking Protocol: Use mocktail for all dependency mocking. STRICTLY prohibit using real implementation dependencies in unit tests.
• Pure Logic: Business logic inside BLoCs or UseCases should be extracted to static pure functions for 100% unit test coverage.

Widget Testing

• Write widget tests for all major UI components
• Test user interactions and state changes
• Widget Keys: Use Key('feature_action_id') format on interactive widgets for test access
• Test Localization: Use AppLocalizations (context.l10n) in widget tests — no hardcoded strings

Integration Testing

• Use IntegrationTestWidgetsFlutterBinding.ensureInitialized() at the start of integration tests
• Interact with widgets via Key (e.g., find.byKey(const ValueKey('increment')))
• Use pumpAndSettle() to wait for animations and async operations to complete
• Run with: flutter test integration_test/

Test Naming & Structure

• Test Naming: Use string interpolation for test group names: group('$ClassName', not group('ClassName',. This ensures consistency and enables better tooling support.
• Test Grouping: Use group() to organize tests by feature, class, or state for clearer reporting.
• Descriptive Names: Test names should clearly describe what is being tested and why.

Common Test Errors

• A RenderFlex overflowed... — Wrap widget in Expanded or constrain dimensions in test
• Vertical viewport was given unbounded height — Wrap ListView in SizedBox with fixed height in test
• setState called during build — Defer state changes to post-frame callback

Running Tests

• flutter test — Run all unit and widget tests
• flutter test test/path/to/file_test.dart — Run specific test file
• flutter test integration_test/ — Run integration tests
• flutter test --coverage — Run with coverage report