Level Up Your Flutter Development with Patrol

Patrol is an open-source testing framework created by LeanCode specifically for Flutter applications. It builds on top of Flutter’s existing testing functionalities to provide more comprehensive testing capabilities.

Integration testing is essential for Flutter apps because it checks how different components like widgets, databases, and services work together seamlessly as a whole, mimicking real user interactions on an actual device. This helps catch bugs that arise from communication issues between components, ensuring a robust and well-functioning app.

It lets you write tests that interact with device features like permissions, notifications, and even change settings. This helps test how your app integrates with the underlying platform.It makes it easier to locate specific widgets within your app’s UI during tests. This improves test writing efficiency and readability.

Table of Contents

Integration Testing with Patrol

What is Integration Testing?

Configuring Patrol for Your Flutter App

Installing the Patrol Package

To use patrol for integration testing in your Flutter project, simply add the patrol package to your pubspec.yaml file and run flutter pub get to download and integrate it.

dependencies:
 patrol: ^latest_version

Writing Your First Patrol Test

With Patrol in your project, lets start writing tests.Create a new test file, import Patrol, and structure your tests like regular Flutter tests – but with the bonus of controlling native UI elements.

import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:patrol/patrol.dart';

void main() {
 // Define the PatrolTester outside of the setUpAll to ensure it's accessible throughout the test suite.
 late PatrolTester patrol;

 setUpAll(() async {
   // Initializes the PatrolTester instance before running any tests.
   patrol = await PatrolTester.init();
 });

 // Use `patrolTest` instead of `testWidgets` when using Patrol for testing.
 // This function is designed to work seamlessly with Patrol functionalities.
 patrolTest(
   'should tap on the button and open a new page',
   // The tester parameter is still of type WidgetTester, allowing you to use familiar flutter_test functions.
   (WidgetTester tester, PatrolTester patrol) async {
     // Ensure your MyApp widget is pumped into the testing environment.
     await tester.pumpWidget(MyApp());

     // Use patrol to interact with the app. This example taps on a button with the text 'Open Page'.
     await patrol.tap(find.text('Open Page'));

     // Settles the animation and rebuilds the widget tree before proceeding.
     await tester.pumpAndSettle();

     // Verifies that after tapping the button, a widget with the text 'Page Opened' is present in the widget tree.
     expect(find.text('Page Opened'), findsOneWidget);
   },
 );
}

In this example,Our Patrol test uses a PatrolTester to tap a button (like a user would) and then checks if the expected result happens.

Leveraging Patrol’s Custom Finders

Patrol comes with a new custom finder system which itself is a game changer,it greatly simplifies writing both widget and integration UI tests.

Let’s look at an example of how Patrol’s custom finders can be used in a test:

testWidgets('should toggle dark mode', (WidgetTester tester) async {
 await patrol.pumpWidget(MyApp());
 await patrol.tap(patrol.find.byTooltip('Toggle Dark Mode'));
 await patrol.pumpAndSettle();

 // Verify dark mode is enabled
 expect(patrol.find.byType(DarkModeWidget), findsOneWidget);
});

This test finds a tooltip in the native UI using a custom finder, taps it, and then checks if the DarkModeWidget appears, confirming dark mode activation.

Benefits of Using Patrol’s Custom Finders

Here are some benefits of using Patrol’s custom finders for integration testing in Flutter apps:

Improved Readability: Patrol’s custom finders use more descriptive names compared to Flutter’s default finders. This makes your tests easier to understand and follow, especially for those who are new to the codebase.
Reduced Verbosity: Custom finders can often combine multiple conditions into a single, concise statement. This reduces the boilerplate code in your tests, making them more streamlined and less cluttered.
Maintainability: As your app’s UI evolves, custom finders can help isolate the logic for finding specific widgets. This makes it easier to update tests when the UI structure changes, promoting better maintainability.
Flexibility: Custom finders allow you to create more complex matching criteria based on various widget properties or relationships within the UI hierarchy. This provides greater control over how you locate specific widgets during testing.

Overall, Patrol’s custom finders enhance the readability, maintainability, and flexibility of your integration tests in Flutter.

Patrol or Maestro:Which is better?

Both Patrol and Maestro are popular choices for integration testing in Flutter, but they cater to slightly different needs.

Patrol shines when dealing with native UI elements. It lets you write tests that interact with device features like permissions and notifications, offering a more comprehensive testing experience. Additionally, Patrol’s custom finders make your tests easier to understand and maintain. However, setting up Patrol, especially for iOS, can be trickier.

Maestro offers a simpler setup and potentially more online resources. However, its capabilities for native UI interaction might require additional tools. Additionally, Maestro tests are written in a separate language, potentially limiting control over your app’s internal workings.

Flutter Patrol CLI: Supercharge your Integration Test

Patrol also has a cli tool called patrol_cli which makes working with patrol easier.

You can install the package from the command line:

dart pub global activate patrol_cli

To use, you can type the following command

$ patrol

Conclusion

In conclusion,Patrol streamlines integration testing in Flutter. It lets you write tests that interact with both your app’s UI and native elements, leading to more robust and reliable apps. While best practices ensure efficient Patrol tests, remember that even the best tools can’t eliminate the inherent complexities of app development.