Getting Started with Visual Testing for Mobile Apps

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You have a range of methods at your disposal, spanning from manual testing and unit tests to functional and end-to-end tests. Each testing technique contributes additional value to the project, enhancing its overall quality. However, some of these methods tend to be conflated or misapplied. Fortunately, the solution lies in visual regression testing, offering an optimal means to ensure the highest quality of UI elements. 

What is Visual Testing?

Visual testing, also known as visual user interface testing, is a method of verifying various UI aspects of software applications. Applications are primarily evaluated based on their visual appearances, graphical interfaces, and overall behavior. Visual testing ensures that software apps look right and detects issues on mobile apps and websites. 

Its primary goal is to verify that every element displayed on the page appears correctly in terms of shape, size, and positioning. This meticulous examination aids developers in crafting a cohesive and consistent user experience. Through this testing, discrepancies or errors between expected and actual on-screen displays can be promptly identified. Ultimately, this ensures that the product meets usability standards and performs optimally across various platforms.

Hence, visual testing serves as a valuable means to validate the intended functionality of the UI and ensure its visual excellence across devices.

Incorporating visual tests into the testing process guarantees an optimal user experience for individuals using different devices, browsers, and versions. This commitment to enhancing the user experience and satisfaction contributes to bolstering customer loyalty. Therefore, integrating visual tests into the testing regimen offers substantial advantages for any organization.

What sets Visual Testing apart from Functional Testing?

Functional testing verifies whether the application aligns with the specified functional requirements or criteria, ensuring its expected operation. Put simply, it assesses whether the application performs as intended. On the other hand, visual testing concentrates on evaluating the appearance and user experience of the application, aiming to uncover any discrepancies or inconsistencies in its design or layout.

Visual testing specifically targets and exposes visual defects such as alignment errors, rendering discrepancies, layout issues, font modifications, responsive design faults, and more. These visual anomalies are distinct and often go undetected during functional testing, highlighting the unique value of visual testing in ensuring a polished and consistent user interface.

What does Visual Testing entail for Mobile Apps?

In the realm of modern app development, developers grapple with the challenge of crafting mobile applications that seamlessly adapt to a diverse range of web browsers, devices, and operating systems. 

Visual testing for mobile applications assumes a crucial role in this intricate process. It scrutinizes the visual components embedded within a mobile app, comparing them against the anticipated design outcomes.

This approach not only ensures the proper functionality of all components but also guarantees an appealing and user-friendly appearance of the app across various browsers, devices, and mobile platforms.

Why opt for visual testing?

Within the realm of mobile application development, various methods exist for testing the UI. However, visual testing emerges as the most accurate and expedient approach. This method empowers app developers to automate the verification of views, significantly expediting the process. It facilitates the confirmation of whether specific components render correctly and guards against regression issues. Detecting bugs becomes more rapid, enabling testers to allocate additional time to scrutinize other facets of the app.

Each test can meticulously examine whether a particular element possesses the intended properties. Even the smallest alterations in color, positioning, or framing might evade a developer’s notice during a code review. However, automated visual tests are adept at pinpointing such changes, ensuring the UI of your app remains consistently “pixel perfect.”

By writing just a few lines of code, an engineer can check several distinct views, thereby reducing the volume of test code. This streamlined approach enhances clarity and readability, which hold particular significance in large projects entrenched in extensive legacy code. Setting up a new testing environment in such scenarios might be time-consuming, but visual tests offer a means to automate this process, ultimately saving considerable time for testers.

But how exactly do visual tests function?

How do visual tests operate?

Visual testing serves as a technique for identifying alterations in UI appearance that might result in regressions. The fundamental process involves comparing the current UI with stored reference snapshots of that UI. This necessitates running a specialized test suite to generate these reference snapshots, which are then stored in the memory of the respective device. Consequently, this procedure must be executed separately on each device.

Following the creation of reference snapshots, the primary test suite validates the current UI state by comparing it against these snapshots. Upon running the tests, a report is generated summarizing the outcomes. Visual testing tools precisely identify discrepancies between the actual UI and the expected results captured in the snapshots. As the UI undergoes changes, the reference snapshots need periodic updating to maintain accuracy.

Tools for visual tests

  • Android: The Android Testing Support library lacks built-in visual testing tools, compelling developers to create their own solutions. A notable framework is “screenshot-tests-for-android” developed by Facebook. This framework facilitates testing entire screens or smaller UI elements like individual controls. 

Runtastic has improved CI support, Android 6.0 compatibility, and made minor enhancements to the project. The library also incorporates a plugin for easy access to generated test reports.

  • iOS: Similar to Android, Apple doesn’t offer native tools for snapshot tests. Consequently, developers must explore external options. Facebook introduced “FBSnapshotTestCase,” now maintained by Uber under the name “iOSSnapshotTestCase.” Presently, this stands as the most reliable visual testing solution for Apple devices.
  • React Native: Jest is the prevalent tool for snapshot testing React Native apps. It allows testers to detect unexpected interface changes within the application, spanning API responses, UI elements, logs, or error messages. Another tool, Loki, primarily used in web development, has found applications in React Native despite limited configuration options. To conduct effective tests, developers must execute them on the same simulator with consistent screen sizes.

Steps in Visual Testing for Mobile Apps

If you aim to pinpoint the visual glitches that could impact your mobile app’s user-friendliness, delving into effective visual testing stands as the right approach. Here’s a breakdown of the steps to conduct visual testing for mobile apps:

  • Define the testing scope: Determine the visual aspects requiring testing in your mobile app, including layout, typography, colors, images, and animations.
  • Choose a testing approach: Decide between manual or automated visual testing. Manual testing involves visually inspecting the app across various devices and screen sizes, while automated visual testing utilizes tools or frameworks to generate and compare screenshots against baseline images.
  • Set up your testing environment: Ensure access to necessary devices, operating systems, and testing tools.
  • Create a baseline image: Develop a set of reference images that represent the anticipated visual appearance of your mobile app, either manually or via automated visual testing tools.
  • Execute tests: Interact with your mobile app and compare its actual visual appearance against the baseline image.
  • Analyze the results: Identify any visual disparities between the actual and expected screenshots of your mobile app.
  • Rectify visual bugs: Once identified, collaborate with your development team to address and resolve these visual discrepancies.

Manual versus Automated Mobile Visual Testing – Choosing the Right Approach

Relying solely on manual visual testing can be time-consuming and prone to errors. It involves testers visually examining the UI for defects, a subjective task susceptible to human error. This subjectivity can lead to inconsistencies, quality issues, and a slower testing process.

Additionally, manual testing across diverse devices, browsers, or locales can encounter time limitations. The subjective nature of defect identification may result in varied interpretations among testers, posing challenges in establishing a clear standard for the expected UI appearance.

As applications become more complex, manual testing becomes increasingly challenging and sluggish, potentially causing delays in software delivery timelines.

Transitioning to automated visual testing can streamline the entire mobile app testing process and mitigate the challenges associated with manual testing. Automated tools can capture, and compare screenshots, identify visual discrepancies, log defects, and execute tests repetitively without additional manual intervention.

This approach excels at detecting even minute visual differences that might go unnoticed in manual mobile visual testing. Adopting automated visual testing not only saves time but also enhances efficiency, contributing to an overall improvement in the mobile testing process.

Where to Implement Automated Visual Testing for Mobile Apps?

Automating visual testing for mobile apps encounters significant hurdles within local grids. Conducting visual tests locally often faces limitations in scalability, making it challenging to encompass a wide range of devices, operating systems, and browsers necessary for comprehensive testing.

Moreover, local grids might lack the advanced AI capabilities crucial for efficient and accurate visual regression testing, limiting their effectiveness in identifying subtle visual differences. Conversely, leveraging cloud-based testing platforms proves strategic for testers, offering the essential scalability required to test mobile apps across diverse device types and configurations.

This flexibility ensures comprehensive coverage and enables testers to effectively replicate real-world scenarios. Cloud-based solutions address local grid limitations by providing infrastructure for parallel testing, facilitating quicker test execution. Many such platforms integrate AI-powered capabilities into their visual testing processes. This integration empowers testers to detect nuanced visual variations with higher precision, contributing to a more thorough and reliable testing strategy.

Implementing Automated Visual Testing for Mobile Apps on Cloud

Cloud-based testing solutions like LambdaTest introduce  AI-powered Smart UI testing platforms, revolutionizing the detection of visual UI regression bugs. LambdaTest’s AI-driven visual testing excels at simplifying intelligent image-to-image comparisons and the detection of visual inconsistencies in elements such as text, layout, color, size, padding, and element positioning.

LambdaTest is an AI-powered browser testing platform that allows users to perform live and automated testing across a vast spectrum of over 3000 environments and real devices. LambdaTest stands out due to its adaptability in supporting automated visual testing with mobile app testing frameworks, including Appium, across a scalable mobile device lab encompassing real Android and iOS devices. This flexibility extends to various programming languages, including Java, Node.js, and C#.

Advantages of visual testing

Visual testing methodologies offer several significant advantages, primarily centered around expedited bug identification and regression prevention. This process encourages developers to uphold a higher standard of UI quality across a diverse array of devices. Detecting UI issues also provides invaluable feedback for designers, enabling them to refine their design strategies for various screen sizes or resolutions. 

Moreover, visual tests excel in uncovering specific view-related edge cases on particular devices, a task that can be time-consuming when performed manually. In summary, the key benefits of visual testing include:

  • Swift bug detection
  • Enhanced code and UI quality
  • Reduced regression occurrences
  • Management of views across varied devices
  • Valuable feedback loop for designers
  • Code streamlining
  • Easy implementation with a low entry barrier
  • Decreased workload for testers
  • Rapid implementation
  • Automation

Conclusion

Visual tests streamline bug detection within your application, offering a substantial acceleration in development. Their multitude of advantages, when properly implemented, guarantee superior quality for your product.

From the standpoint of application quality, visual testing yields numerous advantages recognized by quality assurance specialists. These tests diminish the time spent rectifying bugs, allowing testers to concentrate on other aspects of app evaluation. The proper integration of visual tests enhances the quality of other features, mitigating the prevalence of basic functionality bugs.

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