Dj2695 Custom Copilot Flutter Testing

Flutter Testing

Testing patterns for Flutter apps with BLoC/Cubit, Clean Architecture, bloc_test, and mocktail.

When to Use

• Writing BLoC/Cubit, widget, or integration tests
• Mocking dependencies with mocktail
• Testing Clean Architecture layers
• Setting up test coverage or TDD workflow

Test Types

Dependencies

dev_dependencies:
  flutter_test:
    sdk: flutter
  bloc_test: ^9.1.0
  mocktail: ^1.0.0
  integration_test:
    sdk: flutter

BLoC/Cubit Testing

import 'package:bloc_test/bloc_test.dart';
import 'package:mocktail/mocktail.dart';

class MockRepository extends Mock implements FeatureRepository {}

blocTest<FeatureCubit, FeatureState>(
  'emits [loading, loaded] on success',
  build: () {
    when(() => mockRepo.getData(any()))
        .thenAnswer((_) => TaskEither.right(mockData));
    return FeatureCubit(mockRepo);
  },
  act: (cubit) => cubit.loadData('id'),
  expect: () => [
    const FeatureState(status: Status.loading),
    FeatureState(status: Status.loaded, data: mockData),
  ],
  verify: (_) => verify(() => mockRepo.getData('id')).called(1),
);

Details: BLOC_CUBIT_TESTING.md

Widget Testing

import 'package:flutter_test/flutter_test.dart';
import 'package:mocktail/mocktail.dart';

class MockFeatureCubit extends Mock implements FeatureCubit {}

testWidgets('displays data when loaded', (tester) async {
  final mockCubit = MockFeatureCubit();
  when(() => mockCubit.state).thenReturn(
    FeatureState(status: Status.loaded, data: mockData),
  );

  await tester.pumpWidget(
    MaterialApp(
      home: BlocProvider(create: (_) => mockCubit, child: FeaturePage()),
    ),
  );

  expect(find.text('Expected Data'), findsOneWidget);
});

testWidgets('handles tap', (tester) async {
  await tester.tap(find.byKey(Key('button')));
  await tester.pumpAndSettle();
  verify(() => mockCubit.loadData()).called(1);
});

Details: WIDGET_TESTING.md

Integration Testing

import 'package:integration_test/integration_test.dart';

void main() {
  IntegrationTestWidgetsFlutterBinding.ensureInitialized();

  testWidgets('complete user journey', (tester) async {
    await tester.pumpWidget(MyApp());
    await tester.pumpAndSettle();

    await tester.tap(find.byKey(Key('nav_button')));
    await tester.pumpAndSettle();

    expect(find.text('Success'), findsOneWidget);
  });
}

Best Practices

✅ Test behavior not implementation • Mock dependencies only • Cover success AND failure • Use descriptive names • Test state transitions • Use verify() for interactions • Add keys to widgets • Use pumpAndSettle() after async

❌ Don't test private methods • Don't mock the thing being tested • Don't skip error tests • Don't use hard-coded delays

Commands

flutter test                    # All tests
flutter test --coverage         # With coverage
flutter test test/path/         # Specific path
flutter test integration_test/  # Integration tests

Mocking Essentials

// Setup
class MockRepo extends Mock implements FeatureRepo {}
when(() => mock.method(any())).thenAnswer((_) => TaskEither.right(data));

// Verify
verify(() => mock.method('arg')).called(1);
verifyNever(() => mock.method(any()));

// Fallback for custom types
setUpAll(() => registerFallbackValue(FakeFeature()));

References

• BLoC/Cubit Testing - State management patterns
• Widget Testing - UI testing and finders
• Mocking Patterns - Mocktail techniques
• Repository Testing - Testing repositories and datasources
• Integration Testing - E2E flows and user journeys
• Clean Architecture - Layer-by-layer testing strategy
• Advanced Patterns - Golden tests, performance, custom matchers

Quick Tips

• Use keys for reliable widget finding
• pumpAndSettle() after async operations
• Mock dependencies, not the thing being tested
• Test both success and failure paths
• Use isA<T>().having() for complex assertions

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