Enhance your mobile app development process with advanced CI/CD strategies. This technical guide covers everything you need to build high-quality apps.
This post is intended for mobile engineers, mobile engineering managers, release engineers, release managers, and CTOs seeking to optimize their mobile app development process. We will discuss the key elements of a mobile CI/CD pipeline and explain their importance.
Whether you're part of an early-stage startup with limited experience in mobile app development, a medium to large enterprise with established teams and processes, or simply interested in learning about best practices and tools for enhancing your mobile app development process, this article will provide valuable insights.
Continuous Integration and Continuous Deployment (CI/CD) offer numerous benefits, such as faster and more frequent releases, improved developer productivity, and reduced risk of human error. Mobile apps, however, face unique challenges that necessitate a robust CI/CD pipeline.
Therefore, an efficient and dependable CI/CD and release process become vital for delivering high-quality apps and addressing the aforementioned challenges.
Now, let's explore how to achieve this with the help of automation and CI/CD.
Continuous Integration (CI) automates the process of building, testing, and deploying code with source control. It enables developers to identify and resolve issues early in the development cycle, reducing time and effort spent on debugging. CI also helps enhance code quality and maintainability by enforcing coding standards and best practices before merging code into the main branch.
The goal of CI is to:
Continuous Integration consists of a series of steps, called a pipeline, that are executed whenever code is pushed to the repository.
Source control is an essential part of setting up the CI pipeline. It enables developers to collaborate on code, track changes, and revert to previous versions if necessary. It also helps maintain a history of the codebase, which is useful for debugging and auditing purposes. Popular source control tools include GitHub, GitLab, and Bitbucket.
This step compiles the code, assembles all the resources (such as strings, icons, and illustrations), and generates a binary. This binary is then used for testing and distribution. Platform-specific nuances must be considered when building apps for different platforms. For example, iOS apps are built using Xcode, which requires a Mac machine, while Android apps are built using Gradle, which can run on any machine.
React Native and Flutter are popular tools for building cross-platform apps. These tools use a single codebase to build apps for both iOS and Android.
Caching and artifact management are crucial components of an efficient CI pipeline, as they significantly impact build times and overall system performance. Caching refers to storing intermediate build artifacts and dependencies for reuse across multiple build runs, while artifact management involves organizing, storing, and retrieving these build artifacts.
By caching intermediate build artifacts, subsequent build runs can reuse them, reducing the time spent on redundant compilation tasks. Additionally, caching dependencies, like third-party libraries and frameworks, can also help speed up the build process, as the pipeline no longer needs to download or build these dependencies from scratch each time.
Artifacts typically include binary files (e.g., APKs or IPAs), symbols files (e.g., dSYMs), and other related assets. By utilizing a dedicated artifact storage solution, such as AWS S3, Google Cloud Storage, or JFrog Artifactory, teams can maintain a centralized repository for their build artifacts, streamlining the retrieval process and simplifying versioning.
Static analysis tools serve as a safety net to catch potential issues that might be overlooked during manual code reviews. They also reduce time spent discussing code style. These tools can be used to identify issues such as:
Adding custom rules to static analysis tools can help detect issues specific to your application. Android Lint, SwiftLint, KTLint, and Detekt enable rule extensions to identify application-specific issues, enforcing coding standards and best practices across your team.
An effective feedback loop for larger teams involves understanding the root cause of issues through postmortems or code reviews, identifying long-term solutions, and then codifying these solutions in custom lint rules to be enforced and automated at the CI layer. This helps avoid repeating mistakes, standardize best practices, and automate processes with continuous integration.
Automated testing is crucial for the CI process, as it allows for early detection and resolution of issues in the development cycle. Automated testing enables:
Automated testing can be divided into multiple pipeline steps, each validating different aspects of the application. Parallelizing these steps can reduce time spent on CI.
Unit tests ensure that individual components of your application function as intended. By validating each component in isolation, it is easier to catch regressions early in the development cycle. Unit tests run quickly, providing faster feedback loops. XCTest for iOS and JUnit and Mockito for Android are widely-used unit testing frameworks.
Test-driven development helps ensure your code works as intended by writing tests before actual code. This approach helps you consider the application requirements and their implementation. It also prevents writing unnecessary code, which can lead to increased complexity and technical debt.
Integration tests confirm that different application components work together correctly. Maestro, Espresso for Android and XCUITest for iOS are popular integration testing tools.
End-to-end (E2E) tests are essential for simulating real-world user interactions with your app. They cover the entire application flow, enabling developers to detect issues from the user's perspective and enhance the overall user experience. Integrating E2E tests into your CI pipeline helps ensure a seamless and enjoyable user experience. Maestro, Appium and Detox are popular E2E testing frameworks for mobile apps.
Visual regression testing is an effective method for ensuring your app appears as intended across various devices and screen sizes. This approach involves comparing screenshots of your app's UI with a baseline, allowing you to detect visual changes that might be missed during manual testing. By identifying UI discrepancies, visual regression testing ensures your app maintains a polished and professional appearance. Paparazzi is an excellent visual regression testing tool for Android and Swift snapshot testing for iOS.
Memory leaks occur when an object, no longer needed, is still referenced by the app, causing it to remain in memory. This can result in performance issues and crashes. Memory leak detection tools aid in identifying and resolving memory leaks before they cause problems. Proactively addressing these issues by incorporating memory leak detection tools into your CI pipeline is a smart strategy. LeakCanary for Android and Xcode Memory Graph Debugger for iOS are popular memory leak detection tools.
Continuous deployment (CD) automatically deploys code changes to various environments such as nightly, alpha, beta and production. It's an extension of continuous integration, where the code is automatically deployed to a staging environment after it passes all the tests in the CI pipeline. CI is crucial to enable CD, as it ensures the code is in a good state before deployment.
The benefits of CD include:
Let's now explore the different components involved in CD:
Versioning involves assigning a unique version name or number to an app to identify the code shipped in the binary. The App Store and Play Store require a version name or number to distribute the apps. It's essential to use a consistent versioning scheme across all your apps to avoid confusion. While both iOS and Android apps require versioning, the schemes for each platform have some differences. Understanding these distinctions is crucial for maintaining consistency and clarity across your app's releases.
For iOS apps, the bundle short version string (e.g.,
1.0.0) and bundle version (e.g.,
1) are used to identify the app binary. The bundle short version string is displayed to users in the App Store to identify the app binary. The bundle version is used to identify the app binary and is not displayed to users.
For Android apps, the version name is a string that usually follows the semantic versioning format (e.g.,
1.0.0) but could be any string. The version code is a monotonically increasing integer incremented for each new app version (e.g.,
1). The version name and code are displayed to users in the Play Store to identify the app binary.
To learn more about semantic versioning, check out our docs on version bumping.
Here's a quick visual of what the version bump would look like for both iOS and Android apps:
Date versioning (e.g.,
2020.01.01) is another standard versioning scheme for iOS and Android apps.
The signing step is essential for verifying the authenticity and integrity of your apps, allowing them to be distributed through app stores.
For iOS app signing, you need to work with the following components:
Certificates: Two types of certificates are involved in iOS app signing: Development and Distribution certificates.
Provisioning Profiles: These profiles link a specific app with a set of devices (for development) or enable distribution via the App Store or other methods (for distribution). There are four types of provisioning profiles:
The provisioning profile includes information about the app, the certificate used to sign it, and the devices that can install it. Note that if you change the certificate, you must create a new provisioning profile.
In the CD pipeline, import the appropriate certificate and provisioning profile into the build environment. The app's binary will be signed using the certificate, and the provisioning profile will be embedded.
For Android app signing, you need to work with the following components:
In the CD pipeline, import the keystore file, key alias, and associated passwords into the build environment. The app's APK/AAB will be signed using the private key from the Keystore.
Here's a sample GitHub workflow for both iOS and Android app signing.
Note: On iOS, the binary must be signed with a development or ad-hoc provisioning profile and certificate to run on a device. In contrast, on Android, the debug app (apk) can be installed directly on a device without any additional steps.
Distribution involves making the app available to users. There are several ways to distribute apps:
App stores and other distribution platforms offer various tracks or channels for app distribution, each serving a specific purpose:
Automation is key to streamlining the distribution process, allowing the team to focus on app development. This enables the team to focus on building the app and not worry about the distribution process. The most common way to automate the distribution process is to use tools like Fastlane, Wolfia, Bitrise, and Runway.
These tools provide a centralized location for managing the distribution process and various levels of automation. For example, fastlane provides a command line interface for managing the distribution process, and Wolfia provides a web interface for managing the distribution process and automates the monitoring and rolling out of the app.
Rolling out an app involves making it available to users in the production track. It's essential to roll out the app to a small percentage of users first and then gradually increase the percentage of users to ensure that the app is stable and ready for production. This is called a phased rollout/staged rollout and reduces the risk of releasing a buggy app to all users. Monitoring the app to ensure it's stable and ready for production is also essential.
Here's a quick visual of what a rollout would look like:
This process of monitoring and rolling out the app to the appropriate track/channel can be automated using tools like Wolfia. Release management is a vital part of releasing a stable app to production. Wolfia automates rolling out the app to the appropriate track/channel and automating the monitoring so that the rollout can be halted if the app crosses the threshold of crashes. This reduces the blast radius and the impact of a bug on your users.
After distributing the app to the appropriate track/channel, monitoring its stability and production readiness is crucial. Proactive identification and resolution of issues help maintain a high-quality user experience and optimal app performance.
We wrote a detailed blog post on monitoring mobile apps if you want to learn more about it.
In a future post, we will explore automating your release train and best practices for on-call rotations to address production issues while minimizing user experience impact.
This post has examined the various steps involved in releasing a mobile app to production, as well as tools and methods for streamlining the process.
Our goal at Wolfia is to help mobile teams release high-quality apps to production quickly and frequently, with reduced risk and effort. We automate the entire release process, providing a centralized location for managing it.
To learn more about Wolfia, visit our website, explore our documentation, or contact us.