Flutter Testing Skill

Description

--- name: flutter-testing-skill description: > Generates Flutter widget tests, integration tests, and golden tests in Dart. Supports local execution and TestMu AI cloud for real device testing. Use when user mentions "Flutter", "widget test", "WidgetTester", "testWidgets", "flutter_test", "integration_test". Triggers on: "Flutter", "widget test", "Dart test", "testWidgets", "WidgetTester", "golden test". languages: - Dart category: mobile-testing license: MIT metadata: author: TestMu AI version: "1.0" --- # Flutter Testing Skill You are a senior Flutter developer specializing in testing. ## Step 1 — Test Type ``` ├─ "unit test", "business logic", "model test" │ └─ Unit test: test/ directory, flutter_test package │ ├─ "widget test", "component test", "UI test" │ └─ Widget test: test/ directory, testWidgets() │ ├─ "integration test", "E2E", "full app test" │ └─ Integration test: integration_test/ directory │ ├─ "golden test", "snapshot", "visual regression" │ └─ Golden test: matchesGoldenFile() │ └─ Ambiguous? → Widget test (most common) ``` ## Core Patterns — Dart ### Widget Test (Most Common) ```dart import 'package:flutter/material.dart'; import 'package:flutter_test/flutter_test.dart'; import 'package:my_app/screens/login_screen.dart'; void main() { testWidgets('Login screen shows email and password fields', (WidgetTester tester) async { await tester.pumpWidget(const MaterialApp(home: LoginScreen())); // Verify fields exist expect(find.byType(TextField), findsNWidgets(2)); expect(find.text('Email'), findsOneWidget); expect(find.text('Password'), findsOneWidget); expect(find.byType(ElevatedButton), findsOneWidget); }); testWidgets('Login with valid credentials navigates to dashboard', (WidgetTester tester) async { await tester.pumpWidget(const MaterialApp(home: LoginScreen())); // Enter credentials await tester.enterText(find.byKey(const Key('emailField')), '[email protected]'); await tester.enterText(find.byKey(const Key('passwordField')), 'password123'); // Tap login button await tester.tap(find.byKey(const Key('loginButton'))); await tester.pumpAndSettle(); // Wait for animations and navigation // Verify navigation expect(find.text('Dashboard'), findsOneWidget); }); testWidgets('Shows error for invalid credentials', (WidgetTester tester) async { await tester.pumpWidget(const MaterialApp(home: LoginScreen())); await tester.enterText(find.byKey(const Key('emailField')), '[email protected]'); await tester.enterText(find.byKey(const Key('passwordField')), 'wrong'); await tester.tap(find.byKey(const Key('loginButton'))); await tester.pumpAndSettle(); expect(find.text('Invalid credentials'), findsOneWidget); }); } ``` ### Finder Strategies ```dart // By Key (best — explicit test identifiers) find.byKey(const Key('loginButton')) find.byKey(const ValueKey('email_input')) // By Type find.byType(ElevatedButton) find.byType(TextField) find.byType(LoginScreen) // By Text find.text('Login') find.textContaining('Welcome') // By Icon find.byIcon(Icons.login) // By Widget predicate find.byWidgetPredicate((widget) => widget is Text && widget.data!.startsWith('Error')) // Descendant/Ancestor find.descendant(of: find.byType(AppBar), matching: find.text('Title')) find.ancestor(of: find.text('Login'), matching: find.byType(Card)) ``` ### Actions ```dart await tester.tap(finder); // Tap await tester.longPress(finder); // Long press await tester.enterText(finder, 'text'); // Type text await tester.drag(finder, const Offset(0, -300)); // Drag/scroll await tester.fling(finder, const Offset(0, -500), 1000); // Fling/swipe // CRITICAL: Always pump after actions await tester.pump(); // Single frame await tester.pump(const Duration(seconds: 1)); // Advance time await tester.pumpAndSettle(); // Wait for animations to finish ``` ### Integration Test ```dart // integration_test/app_test.dart import 'package:flutter_test/flutter_test.dart'; import 'package:integration_test/integration_test.dart'; import 'package:my_app/main.dart' as app; void main() { IntegrationTestWidgetsFlutterBinding.ensureInitialized(); testWidgets('Full login flow', (WidgetTester tester) async { app.main(); await tester.pumpAndSettle(); // Login await tester.enterText(find.byKey(const Key('emailField')), '[email protected]'); await tester.enterText(find.byKey(const Key('passwordField')), 'password123'); await tester.tap(find.byKey(const Key('loginButton'))); await tester.pumpAndSettle(); // Verify dashboard expect(find.text('Dashboard'), findsOneWidget); // Navigate to settings await tester.tap(find.byIcon(Icons.settings)); await tester.pumpAndSettle(); expect(find.text('Settings'), findsOneWidget); }); } ``` ### Golden Tests (Visual Regression) ```dart testWidgets('Login screen matches golden', (WidgetTester tester) async { await tester.pumpWidget(const MaterialApp(home: LoginScreen())); await tester.pumpAndSettle(); await expectLater( find.byType(LoginScreen), matchesGoldenFile('goldens/login_screen.png'), ); }); ``` ```bash # Generate golden files flutter test --update-goldens # Run golden comparison flutter test ``` ### Mocking Dependencies ```dart // Using Mockito import 'package:mockito/mockito.dart'; import 'package:mockito/annotations.dart'; @GenerateMocks([AuthService]) void main() { late MockAuthService mockAuth; setUp(() { mockAuth = MockAuthService(); }); testWidgets('Login calls auth service', (tester) async { when(mockAuth.login(any, any)).thenAnswer((_) async => true); await tester.pumpWidget(MaterialApp( home: LoginScreen(authService: mockAuth), )); await tester.enterText(find.byKey(const Key('emailField')), '[email protected]'); await tester.enterText(find.byKey(const Key('passwordField')), 'pass123'); await tester.tap(find.byKey(const Key('loginButton'))); await tester.pumpAndSettle(); verify(mockAuth.login('[email protected]', 'pass123')).called(1); }); } ``` ### Anti-Patterns | Bad | Good | Why | |-----|------|-----| | No `pumpAndSettle()` after action | Always pump after interactions | Animations not complete | | `find.text()` for dynamic text | `find.byKey()` | Locale/text changes break tests | | Testing implementation details | Test user-facing behavior | Brittle | | No mocking in widget tests | Mock services, repos | Tests hit real APIs | ### TestMu AI Cloud (Integration Tests) ```bash # Run integration tests on LambdaTest real devices # 1. Build app for testing flutter build apk --debug # Android flutter build ios --simulator # iOS # 2. Upload to LambdaTest curl -u "$LT_USERNAME:$LT_ACCESS_KEY" \ -X POST "https://manual-api.lambdatest.com/app/upload/realDevice" \ -F "appFile=@build/app/outputs/flutter-apk/app-debug.apk" # 3. Run via Appium (Flutter driver) # Use appium-flutter-driver for element interaction ``` ## Quick Reference | Task | Command | |------|---------| | Run all tests | `flutter test` | | Run specific file | `flutter test test/login_test.dart` | | Run with coverage | `flutter test --coverage` | | Run integration tests | `flutter test integration_test/` | | Update goldens | `flutter test --update-goldens` | | Generate mocks | `flutter pub run build_runner build` | | Test specific platform | `flutter test --platform chrome` | ## pubspec.yaml ```yaml dev_dependencies: flutter_test: sdk: flutter integration_test: sdk: flutter mockito: ^5.4.0 build_runner: ^2.4.0 ``` ## Deep Patterns For advanced patterns, debugging guides, CI/CD integration, and best practices, see `reference/playbook.md`.

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