An introduction to integration testing

Unit tests and widget tests are handy for testing individual classes, functions, or widgets. However, they generally don't test how individual pieces work together as a whole, or capture the performance of an application running on a real device. These tasks are performed with integration tests.

Integration tests are written using the integration_test package, provided by the SDK.

In this recipe, learn how to test a counter app. It demonstrates how to set up integration tests, how to verify specific text is displayed by the app, how to tap specific widgets, and how to run integration tests.

This recipe uses the following steps:

1. Create an app to test.
2. Add the integration_test dependency.
3. Create the test files.
4. Write the integration test.
5. Run the integration test.

Integration testing requires an app to test. This example uses the built-in Counter App example that Flutter produces when you run the flutter create command. The counter app allows a user to tap on a button to increase a counter.

1. To create an instance of the built-in Flutter app, run the following command in your terminal:

   $ flutter create counter_app

2. Change into the counter_app directory.

3. Open lib/main.dart in your preferred IDE.

4. Add a key parameter to the floatingActionButton() widget with an instance of a Key class with a string value of increment.

   dart

    floatingActionButton: FloatingActionButton(
      key: const ValueKey('increment'),
      onPressed: _incrementCounter,
      tooltip: 'Increment',
      child: const Icon(Icons.add),
    ),

5. Save your lib/main.dart file.

After these changes, the lib/main.dart file should resemble the following code.

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            const Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headlineMedium,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        // Provide a ValueKey to this button. This allows finding this
        // specific button inside the test suite, and tapping it.
        key: const ValueKey('increment'),
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ),
    );
  }
}

You need to add the testing packages to your new app.

To add integration_test and flutter_test packages as dev_dependencies using sdk: flutter, run following command.

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

Output

Building flutter tool...
Resolving dependencies... 
Got dependencies.
Resolving dependencies... 
+ file 7.0.0
+ flutter_driver 0.0.0 from sdk flutter
+ fuchsia_remote_debug_protocol 0.0.0 from sdk flutter
+ integration_test 0.0.0 from sdk flutter
...
  test_api 0.6.1 (0.7.1 available)
  vm_service 13.0.0 (14.2.1 available)
+ webdriver 3.0.3
Changed 8 dependencies!
7 packages have newer versions incompatible with dependency constraints.
Try `flutter pub outdated` for more information.

Updated pubspec.yaml file

# ...
dev_dependencies:
  # ... added depencies
  flutter_test:
    sdk: flutter
  flutter_lints: ^3.0.0
  integration_test:
    sdk: flutter
# ...

1. Create a new directory named integration_test.
2. Add empty file named app_test.dart in that directory.

The resulting directory tree should resemble the following:

counter_app/
  lib/
    main.dart
  integration_test/
    app_test.dart

1. Open your integration_test/app_test.dart file in your preferred IDE.

2. Copy the following code and paste it into your integration_test/app_test.dart file. The last import should point to the main.dart file of your counter_app. (This import points to the example app called introduction.)

   integration_test/app_test.dart

   dart

   import 'package:flutter/material.dart';
   import 'package:flutter_test/flutter_test.dart';
   import 'package:integration_test/integration_test.dart';
   import 'package:counter_app/main.dart';
   
   void main() {
     IntegrationTestWidgetsFlutterBinding.ensureInitialized();
   
     group('end-to-end test', () {
       testWidgets('tap on the floating action button, verify counter',
           (tester) async {
         // Load app widget.
         await tester.pumpWidget(const MyApp());
   
         // Verify the counter starts at 0.
         expect(find.text('0'), findsOneWidget);
   
         // Finds the floating action button to tap on.
         final fab = find.byKey(const ValueKey('increment'));
   
         // Emulate a tap on the floating action button.
         await tester.tap(fab);
   
         // Trigger a frame.
         await tester.pumpAndSettle();
   
         // Verify the counter increments by 1.
         expect(find.text('1'), findsOneWidget);
       });
     });
   }

This example goes through three steps:

1. Initialize IntegrationTestWidgetsFlutterBinding. This singleton service executes tests on a physical device.

2. Interact and test widgets using the WidgetTester class.

3. Test the important scenarios.

The integration tests that run vary depending on the platform on which you test. You can test against a mobile platform or the web.

To test on a real iOS or Android device

1. Connect the device.

2. Run the following command from the root of the project.

   $ flutter test integration_test/app_test.dart

   The result should resemble the following output:

   $ flutter test integration_test/app_test.dart
   00:04 +0: loading /path/to/counter_app/integration_test/app_test.dart
   00:15 +0: loading /path/to/counter_app/integration_test/app_test.dart
   00:18 +0: loading /path/to/counter_app/integration_test/app_test.dart   2,387ms
   Xcode build done.                                           13.5s
   00:21 +1: All tests passed!

3. Verify that the test removed the Counter App when it finished. If not, subsequent tests fail. If needed, press on the app and choose Remove App from the context menu.

To learn more, consult the Integration testing page.

To test in a web browser, perform the following steps.

1. Install ChromeDriver into the directory of your choice.

   $ npx @puppeteer/browsers install chromedriver@stable

   To simplify the install, this command uses the @puppeteer/browsers Node library.

2. Add the path to ChromeDriver to your $PATH environment variable.

3. Verify the ChromeDriver install succeeded.

   $ chromedriver --version
   ChromeDriver 124.0.6367.60 (8771130bd84f76d855ae42fbe02752b03e352f17-refs/branch-heads/6367@{#798})

4. In your counter_app project directory, create a new directory named test_driver.

   $ mkdir test_driver

5. In this directory, create a new file named integration_test.dart.

6. Copy the following code and paste it into your integration_test.dart file.

   test_driver/integration_test.dart

   dart

   import 'package:integration_test/integration_test_driver.dart';
   
   Future<void> main() => integrationDriver();

7. Launch chromedriver as follows:

   $ chromedriver --port=4444

8. From the root of the project, run the following command:

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

   The response should resemble the following output:

   Resolving dependencies...
     leak_tracker 10.0.0 (10.0.5 available)
     leak_tracker_flutter_testing 2.0.1 (3.0.5 available)
     leak_tracker_testing 2.0.1 (3.0.1 available)
     material_color_utilities 0.8.0 (0.11.1 available)
     meta 1.11.0 (1.14.0 available)
     test_api 0.6.1 (0.7.1 available)
     vm_service 13.0.0 (14.2.1 available)
   Got dependencies!
   7 packages have newer versions incompatible with dependency constraints.
   Try `flutter pub outdated` for more information.
   Launching integration_test/app_test.dart on Chrome in debug mode...
   Waiting for connection from debug service on Chrome...             10.9s
   This app is linked to the debug service: ws://127.0.0.1:51523/3lofIjIdmbs=/ws
   Debug service listening on ws://127.0.0.1:51523/3lofIjIdmbs=/ws
   00:00 +0: end-to-end test tap on the floating action button, verify counter
   00:01 +1: (tearDownAll)
   00:01 +2: All tests passed!
   All tests passed.
   Application finished.

   To run this as a headless test, run flutter drive with -d web-server option:

   $ flutter drive \
     --driver=test_driver/integration_test.dart \
     --target=integration_test/app_test.dart \
     -d web-server