Flutter Testing Guide: Unit, Widget, and Integration Tests

lib/
  models/
    user.dart
  services/
    user_service.dart
  widgets/
    user_card.dart
test/
  models/
    user_test.dart       # unit tests
  services/
    user_service_test.dart
  widgets/
    user_card_test.dart  # widget tests
integration_test/
  app_test.dart          # integration tests
pubspec.yaml

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

// lib/models/user.dart
class User {
  final String id;
  final String name;
  final String email;
  final UserRole role;

  const User({
    required this.id,
    required this.name,
    required this.email,
    required this.role,
  });

  bool get isAdmin => role == UserRole.admin;

  User copyWith({ String? name, String? email, UserRole? role }) {
    return User(
      id: id,
      name: name ?? this.name,
      email: email ?? this.email,
      role: role ?? this.role,
    );
  }

  @override
  bool operator ==(Object other) =>
      other is User && other.id == id;
  
  @override
  int get hashCode => id.hashCode;
}

enum UserRole { admin, editor, viewer }

// test/models/user_test.dart
import 'package:flutter_test/flutter_test.dart';
import 'package:my_app/models/user.dart';

void main() {
  group('User', () {
    final alice = User(
      id: '1',
      name: 'Alice',
      email: 'alice@example.com',
      role: UserRole.admin,
    );

    group('isAdmin', () {
      test('returns true for admin role', () {
        expect(alice.isAdmin, isTrue);
      });

      test('returns false for non-admin roles', () {
        final viewer = alice.copyWith(role: UserRole.viewer);
        expect(viewer.isAdmin, isFalse);
      });
    });

    group('copyWith', () {
      test('updates name while preserving other fields', () {
        final updated = alice.copyWith(name: 'Alice Smith');
        expect(updated.name, equals('Alice Smith'));
        expect(updated.email, equals(alice.email));
        expect(updated.id, equals(alice.id));
      });

      test('original is unchanged after copyWith', () {
        alice.copyWith(name: 'Different Name');
        expect(alice.name, equals('Alice'));
      });
    });

    group('equality', () {
      test('users with the same id are equal', () {
        final alice2 = alice.copyWith(name: 'Alice Changed');
        expect(alice, equals(alice2));
      });

      test('users with different ids are not equal', () {
        final bob = User(id: '2', name: 'Bob', email: 'bob@example.com', role: UserRole.viewer);
        expect(alice, isNot(equals(bob)));
      });
    });
  });
}

// lib/widgets/counter_widget.dart
import 'package:flutter/material.dart';

class CounterWidget extends StatefulWidget {
  const CounterWidget({super.key});

  @override
  State<CounterWidget> createState() => _CounterWidgetState();
}

class _CounterWidgetState extends State<CounterWidget> {
  int _count = 0;

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        Text('Count: $_count', key: const Key('count-text')),
        ElevatedButton(
          key: const Key('increment-btn'),
          onPressed: () => setState(() => _count++),
          child: const Text('+'),
        ),
        ElevatedButton(
          key: const Key('decrement-btn'),
          onPressed: () => setState(() { if (_count > 0) _count--; }),
          child: const Text('-'),
        ),
      ],
    );
  }
}

// test/widgets/counter_widget_test.dart
import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:my_app/widgets/counter_widget.dart';

void main() {
  group('CounterWidget', () {
    testWidgets('renders with initial count of 0', (WidgetTester tester) async {
      await tester.pumpWidget(
        const MaterialApp(home: CounterWidget()),
      );

      expect(find.text('Count: 0'), findsOneWidget);
    });

    testWidgets('increments count on + button tap', (WidgetTester tester) async {
      await tester.pumpWidget(
        const MaterialApp(home: CounterWidget()),
      );

      await tester.tap(find.byKey(const Key('increment-btn')));
      await tester.pump();  // rebuild the widget

      expect(find.text('Count: 1'), findsOneWidget);
    });

    testWidgets('does not decrement below 0', (WidgetTester tester) async {
      await tester.pumpWidget(
        const MaterialApp(home: CounterWidget()),
      );

      await tester.tap(find.byKey(const Key('decrement-btn')));
      await tester.pump();

      expect(find.text('Count: 0'), findsOneWidget);  // stays at 0
    });
  });
}

// 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();

  group('App', () {
    testWidgets('user can login and see the dashboard', (tester) async {
      app.main();
      await tester.pumpAndSettle();

      // Find login form
      await tester.enterText(find.byKey(const Key('email-field')), 'alice@example.com');
      await tester.enterText(find.byKey(const Key('password-field')), 'password123');
      await tester.tap(find.byKey(const Key('login-btn')));
      await tester.pumpAndSettle();

      // Should be on dashboard
      expect(find.text('Dashboard'), findsOneWidget);
      expect(find.text('Welcome, Alice'), findsOneWidget);
    });
  });
}

# Unit and widget tests
flutter <span class="hljs-built_in">test

<span class="hljs-comment"># Specific test file
flutter <span class="hljs-built_in">test <span class="hljs-built_in">test/models/user_test.dart

<span class="hljs-comment"># With coverage
flutter <span class="hljs-built_in">test --coverage
genhtml coverage/lcov.info -o coverage/html

<span class="hljs-comment"># Integration tests (device must be connected)
flutter <span class="hljs-built_in">test integration_test/

<span class="hljs-comment"># Integration tests with specific driver
flutter drive --target=test_driver/app.dart