Using fastlane in Flutter to build CI/CD pipeline

As mobile app development becomes more complex, it is important to have a robust Continuous Integration and Continuous Deployment (CICD) pipeline. A well-configured CICD pipeline can help you automate the building, testing, and deployment of your Flutter application. In this article, we will focus on how to use Fastlane to build a CICD pipeline for Flutter applications.

What is Fastlane?

Fastlane is an open-source toolset that provides automation for building, testing, and deploying mobile applications. It was created by Felix Krause and is maintained by a community of contributors. Fastlane aims to simplify the entire mobile app development process by automating tasks such as code signing, creating screenshots, and publishing to app stores.

Fastlane supports both iOS and Android platforms and has built-in integrations with many popular CI/CD tools, such as Jenkins, Travis CI, and Bitrise.

Setting up Fastlane

Before we begin, ensure that you have installed the latest version of Fastlane on your system. You can do this by running the following command in your terminal:

sudo gem install fastlane -NV

Once Fastlane is installed, navigate to your Flutter project directory and initialize Fastlane by running the following command:

fastlane init

This will prompt you to answer a series of questions to set up your Fastlane configuration. You can choose to create a new Fastlane configuration file, use an existing configuration file, or start from scratch.

Using Fastlane to build your Flutter app

The first step in setting up your CICD pipeline is to configure Fastlane to build your Flutter application. To do this, you will need to add a new lane to your Fastfile.

Open your Fastfile and add the following lane:

lane :build do
  # Build your Flutter application
  sh("flutter build apk --release")
end

This lane uses the flutter build command to build your Flutter application in release mode. You can customize this command to build for different platforms or add additional flags, such as --split-debug-info to reduce the size of your APK.

To run this lane, navigate to your Flutter project directory and run the following command:

fastlane build

This will build your Flutter application and generate an APK file in the build/app/outputs/apk/release/ directory.

Running tests with Fastlane

Fastlane can also be used to run tests on your Flutter application. To set this up, add a new lane to your Fastfile:

lane :test do
  # Run your Flutter tests
  sh("flutter test")
end

This lane uses the flutter test command to run all of the tests in your Flutter application. You can customize this command to run specific tests or test suites.

To run this lane, navigate to your Flutter project directory and run the following command:

fastlane test

This will run your Flutter tests and generate a report of the test results.

Deploying your Flutter app with Fastlane

Fastlane can also be used to deploy your Flutter application to the app store. To set this up, you will need to add a new lane to your Fastfile.

Here is an example lane that deploys your app to the Google Play Store:

lane :deploy_to_play_store do
  # Build your Flutter application
  sh("flutter build appbundle --release")

  # Upload your app bundle to the Google Play Store
  playstore(track: 'internal', package_name: 'com.example.app', aab: 'build/app/outputs/bundle/release/app.aab', skip_upload_apk: true)
end

This lane uses the flutter build command to build your app bundle in release mode, and then uses the playstore action to upload the app bundle to the Google Play Store.

Note that you will need to have your Google Play Store credentials set up in your Fastlane configuration for this to work. You can do this by running the following command:

fastlane supply init

This will prompt you to enter your Google Play Store credentials and will create a supply.json file in your Fastlane directory.

To deploy your app to the Play Store, navigate to your Flutter project directory and run the following command:

fastlane deploy_to_play_store

This will build your app bundle and upload it to the Google Play Store.

Conclusion

In this article, We have explored how to use Fastlane to build a CICD pipeline for Flutter applications. I have shown how to build and test your app using Fastlane, as well as how to deploy your app to the Google Play Store.

Fastlane provides a powerful toolset for automating mobile app development tasks, and can help you save time and reduce errors in your development process. By configuring Fastlane to work with your Flutter project, you can build a robust CICD pipeline that will help you deliver high-quality apps to your users.