Flutter Integration Tests

Setup

Add integration_test as a dev dependency:

flutter pub add 'dev:integration_test:{"sdk":"flutter"}'

Required pubspec.yaml entries:

dev_dependencies:
  flutter_test:
    sdk: flutter
  integration_test:
    sdk: flutter

Project Structure

my_app/
  lib/
    main.dart
  integration_test/
    app_test.dart
    feature_a_test.dart
    feature_b_test.dart
  test_driver/                # Only for web testing and performance profiling
    integration_test.dart
    perf_driver.dart

• Place all integration tests in integration_test/.
• Only create test_driver/ when targeting web browsers or capturing performance timelines.

Writing Tests

Binding Initialization

Always initialize the binding before any tests:

import 'package:flutter_test/flutter_test.dart';
import 'package:integration_test/integration_test.dart';
import 'package:my_app/main.dart';

void main() {
  IntegrationTestWidgetsFlutterBinding.ensureInitialized();

  testWidgets('description', (tester) async {
    await tester.pumpWidget(const MyApp());
    await tester.pumpAndSettle();
    // assertions
  });
}

Widget Identification

Add Key or ValueKey to widgets that tests need to find:

// In production code
FloatingActionButton(
  key: const ValueKey('increment'),
  onPressed: _incrementCounter,
  child: const Icon(Icons.add),
)

// In test code
final fab = find.byKey(const ValueKey('increment'));
await tester.tap(fab);

Prefer find.byKey() over find.text() for stability across localization changes.

Core Test Pattern

testWidgets('tap increment, verify counter updates', (tester) async {
  await tester.pumpWidget(const MyApp());

  // 1. Verify initial state
  expect(find.text('0'), findsOneWidget);

  // 2. Perform action
  await tester.tap(find.byKey(const ValueKey('increment')));

  // 3. Wait for UI to settle
  await tester.pumpAndSettle();

  // 4. Verify result
  expect(find.text('1'), findsOneWidget);
});

Grouping Tests

void main() {
  IntegrationTestWidgetsFlutterBinding.ensureInitialized();

  group('counter', () {
    testWidgets('starts at zero', (tester) async { /* ... */ });
    testWidgets('increments on tap', (tester) async { /* ... */ });
  });

  group('navigation', () {
    testWidgets('opens settings page', (tester) async { /* ... */ });
  });
}

Platform-Specific Patterns

Platform-Conditional Imports

When tests differ between web and native platforms:

// example_test.dart
import '_example_test_io.dart'
    if (dart.library.js_interop) '_example_test_web.dart' as tests;

void main() => tests.main();

Create _example_test_io.dart and _example_test_web.dart with platform-specific implementations.

Screenshots

void main() {
  final binding = IntegrationTestWidgetsFlutterBinding.ensureInitialized();

  testWidgets('capture screenshot', (tester) async {
    await tester.pumpWidget(const MyApp());

    // Required on Android before taking screenshots
    await binding.convertFlutterSurfaceToImage();
    await tester.pumpAndSettle();

    final bytes = await binding.takeScreenshot('home_screen');
    expect(bytes.isNotEmpty, isTrue);
  });
}

• Call convertFlutterSurfaceToImage() before screenshots on Android/iOS.
• Web screenshots return empty bytes; handle accordingly.

Golden File Testing

testWidgets('matches golden', (tester) async {
  await tester.pumpWidget(const MyApp());
  await tester.pumpAndSettle();

  await expectLater(
    find.byType(MaterialApp),
    matchesGoldenFile('goldens/home_screen.png'),
  );
});

Performance Profiling

For detailed guidance on performance profiling with traceAction(), timeline recording, and driver setup, see references/performance-profiling.md.

Running Tests

Mobile and Desktop

flutter test integration_test/app_test.dart

Web

1. Create test_driver/integration_test.dart:

import 'package:integration_test/integration_test_driver.dart';

Future<void> main() => integrationDriver();

2. Launch ChromeDriver and run:

chromedriver --port=4444

flutter drive \
  --driver=test_driver/integration_test.dart \
  --target=integration_test/app_test.dart \
  -d chrome

Use -d web-server for headless mode.

CI/CD (Linux)

Use xvfb-run for headless display:

xvfb-run flutter test integration_test -d linux

Best Practices

1. Initialize binding once -- call IntegrationTestWidgetsFlutterBinding.ensureInitialized() at the top of main(), before any testWidgets.
2. Verify initial state -- always assert starting conditions before performing actions.
3. Use pumpAndSettle() after every action -- wait for animations and async operations to complete.
4. Prefer find.byKey() over find.text() -- keys are stable across locales and text changes.
5. Add ValueKey to testable widgets -- plan for testability in production code.
6. Group related tests -- use group() for logical organization.
7. One concern per test -- each testWidgets should verify a single user flow or behavior.
8. Use --profile for performance tests -- never measure performance in debug mode.
9. Use --no-dds on mobile devices -- avoids Dart Development Service conflicts during profiling.
10. Separate platform implementations -- use conditional imports (_io.dart / _web.dart) when behavior diverges.
11. Call convertFlutterSurfaceToImage() on Android -- required before taking screenshots.
12. Clean up test apps on device -- leftover apps can cause subsequent test failures.