“Unfortunately the app has stopped”.
This would be the most annoying system message a user might come across while using your app. For users, it means it’s time to churn and try an alternative. But for mobile app developers, it’s terrible news.
The only way to avoid such unfavourable scenarios is by thoroughly performing mobile testing before and after publishing a mobile app.
Mobile app testing is an unavoidable process of the mobile app development process. It can directly affect an application’s performance, user experience, desirability, and ultimately the number of users who download, engage and retain.
Even if you’re an experienced developer or newbie trying to learn app development, knowing how to approach and perform app testing is integral. After all, a great, error-free application is a prerequisite to be successful with app marketing and win the hearts of your users.
This comprehensive guide will cover the A-Z of mobile testing, including the different types of testing, tools for mobile testing (both free and paid), how to do mobile testing, things you need to keep in mind, the challenges you might encounter, and more.
What Is Mobile Testing?
Mobile testing or mobile app testing is the process of testing applications for their usability, functionality, consistency, and compatibility. Application testing can be performed either manually or with the help of automation.
Why Should You Test Mobile Apps?
Rigorously testing an application will ensure that the number of bugs and other usability issues is minimized – enabling users to experience the app without any hindrance. An adequately tested app will increase user satisfaction, drive app installs organically and will work wonders for retaining and engaging the existing users.
Types of Mobile Testing
1. Usability Testing
Usability testing, also known as UX testing, is a method used to measure how user-friendly and intuitive an application is. This test evaluates how easy it is for users to reach specific app goals, for example, completing a purchase in an e-commerce application.
Along with identifying bugs that bug the user, usability testing will also focus on delivering suggestions that can improve the app experience. Usability tests are performed by QA testers on real devices by mimicking the real-world scenarios an end-user might encounter.
2. User Acceptance Testing (UAT)
User acceptance testing (UAT) is a crucial part of mobile app development and can significantly affect its success. As the name implies, UAT involves sending the application to real users and allowing them to use it in real-world situations.
This will allow you to gain invaluable insights and understand how the end-users are experiencing the application. UAT is also known as end-user testing or beta testing, and its primary purpose is to identify whether the app is capable of meeting the end-users’ expectations.
3. UI Testing
UI testing is the process of testing the user interface elements of an app to ensure whether they meet the expected performance and functionality. It involves testing all graphical elements such as the text boxes, hamburger menus, fonts, colours, checkboxes, and more.
4. Functional Testing
As the name suggests, functional testing checks whether the functionalities work as described in the app requirement document or not. Functional testing ensures that all the features deliver precise outputs for the appropriate inputs.
5. Compatibility Testing
Compatibility testing is a kind of non-functional mobile testing performed to ensure that an application seamlessly works on different operating systems, devices, networks, and varying hardware specifications.
There are two other types of compatibility testing known as backwards and forwards compatibility testing, which will test the mobile app’s compatibility with older and newer software versions, respectively.
6. Performance Testing
Performance testing examines how well the app performs under specific workloads. This test will help in determining the speed and stability of the app and will also help in identifying the functions that slow down the app performance.
Performance testing can be further divided into the following.
- Load Testing – It is performed to determine whether the application can handle the expected usage by simulating multiple users accessing the app simultaneously.
- Stress Testing – It is executed to verify whether the app remains stable and reliable when the use is beyond the expected workloads.
- Endurance Testing – It is performed to ensure that the app’s performance doesn’t drop below a particular level with sustained activity over a long period.
- Spike Testing – It is performed to determine how the app’s performance or behaviour will be affected by a sudden increase in the number of users.
- Volume Testing – It is executed to check how the app’s performance is affected when there is a large volume of data in the database.
7. Installation Testing
Installation testing, also known as implementation testing, is a mobile testing technique performed to check whether the app installs and uninstalls properly. It will also ensure the app updations are performed error-free.
8. Security Testing
For app users, security and confidentiality of their personal information is a top priority. Nearly 81% of all mobile users feel that safeguarding their personal data is critical. This makes security testing an unavoidable part of mobile development and can heavily contribute to an application’s success.
In principle, security testing is a mobile testing technique that uncovers the vulnerabilities of an application. Since the majority of apps require one or the other form of personal data, security tests are conducted to ensure the confidentiality of data and to reassure that the application is capable of protecting itself from hackers and information leaks.
Security testing can be further divided into,
- Vulnerability Scanning – It detects and classifies the vulnerabilities by scanning all features that can be exploited.
- Penetration Testing – It involves attempts to exploit the vulnerabilities of an application and to try whether unauthorized access is possible.
- Security Scanning – It tries to identify the weaknesses in the app’s security and tries to offer solutions to reduce the risks.
- Security Auditing – It involves evaluating an app’s risk level with respect to a set of standards as laid down by the industry.
9. Localization Testing
It is a mobile application testing approach in which the app is tested for different geographical locations. Since the majority of apps have a global user base, localization testing will ensure that the localized features are activated and function correctly in different locations.
Localized features could include different UI languages, cultural appropriateness of UI, varying currencies for in-app purchases, and even content restrictions based on local regulations. It is also sometimes referred to as L10N testing – 10 being the number of characters between L and N in the word localization.
10. Memory Leakage Testing
Memory leakage is a condition in which the application fails to return the memory it has borrowed for temporary use. In a simpler sense, memory leaks happen when you hold on to an object even after its purpose has been completed.
Memory leaks usually occur due to bugs in the code, and this test is aimed to identify such leaks. Memory leakage testing is performed on multiple devices with varying memory capabilities so that testers can check the difference in app performance in each device.
11. Interrupt Testing
Interrupt testing checks how an app reacts to incoming phone calls, SMS, unexpected shutdowns, lower battery levels, and system notifications. Image Credit: medium.com
This type of testing checks how the app responds to unexpected interruptions. Depending on the nature of interruption, the application must be capable of pausing and returning to its original state without losing data.
Interruptions could include,
- Incoming phone calls
- Incoming messages or push notifications from other apps.
- Device shutting down while the app is running.
- Low battery levels when the app is running.
12. Recovery Testing
As the name suggests, recovery testing is a non-functional testing technique that verifies an app’s ability to recover from failures such as network failures, or software or hardware crashes. The primary purpose of this testing to determine whether the app can continue its operation once the integrity of the system is lost.
How to Craft a Successful Mobile Testing Strategy
The first step towards creating a successful mobile testing strategy is to understand the possible challenges you might encounter before and after publishing your application on the app stores. One such challenge would be the ever-increasing number of mobile devices, screen sizes, and OS customization.
Similarly, knowing your target audience is critical for crafting a testing strategy. Only then can you confidently choose and list the mobile devices with the highest priority and the ones you can afford to miss.
If you’d like to know more about the importance of understanding your target audience and market, check out our comprehensive article about finding the perfect target audience for mobile apps.
Once you’re aware of your target audience, proceed to the following steps for rightly testing mobile applications.
1. Define the Test Coverage
The first and most crucial step of application testing is defining the app features and functionality you’re planning to test. This will help you determine the types of mobile testing you’ll have to adopt – for example, usability, functional, or security testing.
2. Manual or Automated Testing
Many view manual and automated mobile testing as two opposite testing methods. Although it is true in the literal sense, app creators have to embrace both.
They complement each other and only by combining both can a developer understand the true flaws and strengths of their creation. Let’s take a look at both.
i) Manual Mobile Testing
Manual testing is the most elementary type of mobile testing that requires human testers to conduct tests manually. Quality assurance (QA) specialists carry out this testing method without the help of automated tools, scripts, or extensions.
Manual testing can be incredibly time-consuming and monotonous – but it’s an unavoidable part of app testing. As these tests are performed by trained professionals, they are also likely to provide valuable comments on the user experience of the application.
Manual tests will also help developers to understand the bugs and errors in terms of the app’s concept. This will also allow them to understand the feasibility of each feature and to make an informed decision on whether to remove or retain certain features.
ii) Automated Mobile Testing
Automated mobile app testing is the type of testing that uses tools to assess the performance of an application and to uncover errors that may affect its user experience and performance. To run automated tests, QA testers use tools (discussed later), scripts, and extensions.
Unlike manual mobile testing, automated testing is performed without any human supervision and is ideal for testing features that require multiple tests to be performed simultaneously. Automation is also useful for running tests 24X7.
Automated tests are also reusable – meaning, developers can repeat automated tests, n number of times, even if the source code is changed. Automation mobile testing tools also increase the reliability of test results as human errors are eliminated from the equation.
However, there are many situations where automated testing isn’t feasible. For instance, during mobile game development, the test cases associated with games will be too complicated for automated testing.
As the game design will contain a variety of UI elements (gigantic in number as compared to a non-gaming app) they will require a real user to tap, swipe, tilt and perform other kinds of gesture.
Although these movements can be automated, it will be incredibly expensive as you’ll have to account for each possible gesture or movement.
You can also combine both testing methods for better results, for instance, by establishing a ratio (say 60/40) between the time and resources you’ll be spending on each approach.
3. Choose the Devices
Although the smartphone market (especially the Android market) offers a wide variety of devices, you aren’t obligated to test on all of them. You only have to choose those devices that your target market is more likely to use.
For that, you can list the age groups, geographics, income status and other critical demographic information of your target market to find the screen sizes, preferred OS, and price range of the devices.
4. Choose Between Real Devices or Emulators or Simulators
As you know, real devices are smartphones that your target audience might use. If not for real devices, you can test your app on emulators and simulators as well.
The difference between emulator and simulator in mobile testing is that an emulator is essentially a desktop application, capable of mimicking the hardware and OS for running and testing applications.
Whereas a simulator doesn’t mimic the hardware or OS – instead, it mimics the fundamental behaviour of a device. Although simulators have a more straightforward functionality, they are not as effective as emulators for testing applications.
In the case of real devices, you will have to pay to obtain them and so will be an expensive procedure. Whereas emulators and simulators are generally free and you’ll have to just download and install them.
However, testing on real devices will give you more accurate results as compared to emulators or simulators. This is because simulators and emulators are not capable of simulating all kinds of user interactions.
Simulators and emulators can’t mimic critical features such as a smartphone’s camera and battery and aren’t capable of delivering realistic simulations of smartphone memory usage. Also, their processing speeds are slower as compared to real devices.
However, debugging is easier with emulators and simulators. They generally offer solutions for debugging an application and also for capturing screenshots whenever an app runs into an error.
In short, going for real devices will give you more accurate results, but obtaining and maintaining them can be expensive. Although simulators and emulators are cheaper and have debugging capabilities, they are prone to deliver false positives.
5. Choose Between In-House or Cloud
Cloud testing eliminates the need for acquiring and maintaining a plethora of smartphones. Cloud mobile testing can be performed with the help of simulators or emulators, or with the use of smartphones hosted in the cloud.
Cloud testing allows the testing teams to run as many tests as they want (at the same time) without the limitations of any local infrastructure. They can also test on multiple devices at a time, instead of testing sequentially on different devices.
However, if your app contains certain elements eligible for patents and so don’t want to take any chance with security, then opting for an in-house testing solution is ideal. This will make sure all the testing data stays within the premise, but the limitations regarding testing capacity will be a notable downside.
6. Track and Rectify Errors
After running the tests, you’ll have information about the errors that need to be rectified. As a best practice, list the errors in terms of priority and rectify the most critical ones first. For example, a feature that crashes frequently requires more attention than a misspelt app icon.
Generally, errors can be classified into,
- Low Priority – Has minimal impact on functionality.
- Medium Priority – A functionality isn’t working as expected, but the user can work around it.
- High Priority – A critical functionality isn’t working, but the user can work around it.
- Blocker – A critical functionality isn’t working, and the user can’t proceed further.
Mobile Testing Best Practices
1. Test as Early and Often as Possible
Start testing your application as soon as its critical features and logic is working. This will help you find and rectify errors early on that will otherwise become costly to fix.
2. Know Your App and Your Audience
As previously mentioned, knowing your target audience is crucial to building an app that users will cherish and find useful.
You need to fully understand the functionality and architecture of your application before starting with testing – which will allow you to understand the errors from the perspective of a typical user. Knowing the app will also help you to construct relevant test cases.
3. Consider Real-World Scenarios
Although QA testers are keen to include test cases that would depict real-world scenarios, they must also consider specific test conditions such as,
- Interruptions caused by low battery warnings, SMS, and alarms.
- Unreliable internet connections.
- Differences in time zones.
- Change in notification settings such as the use of “Do not disturb” mode.
4. Be Aware of the Upcoming OSs and Upgrades
Although Android and iOS are forecasted to dominate the global market of mobile operating systems for the upcoming years, it will be naive not to consider the chances of another OS coming into dominance.
For instance, Huawei recently released an open-source mobile OS called Harmony OS. Similarly, existing operating systems are often upgraded, and so, developers must ensure that their applications are compatible with every new upgrade.
5. Test on Smartphones With Varying Hardware Features
As repeatedly mentioned before, smartphones with drastically different configurations rule the market, and so you’ll have to test your applications on the majority of them. Of course, you can take advantage of cloud testing or narrow down the smartphone choices by looking at the target market.
Top Mobile Testing Tools
Appium is a popular open-source automation tool for mobile testing – ideal for testing native, hybrid, and web applications. It can also be used for cross-platform app testing and can run on real devices, emulators and simulators.
Appium is easy to set up on multiple platforms and supports numerous programming languages, including Java, PHP, Node, and Python. It can be readily integrated with third-party tools and can also control browsers like Chrome and Safari.
TestComplete is an automated mobile testing tool that lets you create, manage, and execute UI design tests for mobile applications. It is an AI-integrated tool and allows you to test devices without jailbreaking.
Kobiton is a cloud-based mobile testing software application that lets you run manual and automated tests on real devices. It’s built on top of the Appium framework and supports GPS simulations, multi-touch gestures, screen orientation, and device connection management.
Kobiton makes it possible to test across multiple devices without modifying the script. It also has a centralized testing test history and data log for efficient collaboration. For quick identification of errors, screenshots and metadata are automatically generated.
4. Monkey Talk
Image Credit: alignminds.com
Monkey Talk is an open-source mobile app automated testing tool that lets you run functional interactive tests on iOS and Android apps. You can use it without a solid understanding of programming or scripting – making it ideal for beginners relying on no-code app builders.
Monkey talk will automatically capture screenshots whenever an error occurs and is suitable for native, hybrid, and web apps. You can also generate HTML and XML reports using this tool.
Espresso is a Google mobile testing tool that offers APIs for writing UI tests. It is integrated with the Android Studio and supports all kinds of Android instrumentation. Using Espresso, you can run tests on both emulators and real devices.
Espresso also offers a feature called Espresso Test Recorder that lets you record mobile app tests. Although it is a platform-specific solution, Espresso provides a flexible and straightforward API and also allows you to create tests using Java and Kotlin.
That’s just the tip of the iceberg. Check out our killer article about the top 25 mobile testing tools to know more about the free and paid automation tools you can use for mobile testing.
Common Mobile Testing Challenges
1. Variations in Screen Sizes
This might be the top among the unique challenges to testing mobile applications. With users demanding more vividness (which translates to higher pixel density), manufacturers have no other choice but to introduce advanced displays on the smartphone line.
Towards the end of 2020, Sony released a new smartphone, the Xperia 1 II with 4K screens. Dozens of screen sizes and the introduction of bezel-less design can be a headache for testers due to multiple aspect ratios.
Even Google’s Material Design has listed numerous device screen metrics for that matter.
2. Device Fragmentation
Just like the screen size, smartphones come in different sizes, shapes and with varying hardware. This will be one of the biggest challenges of mobile testing as QA testers will have to make sure the application works perfectly on them all – at least on the majority of them.
Device fragmentation is more challenging in the Android realm as more than 1,300 original equipment manufacturers (OEMs) have developed more than 24,000 devices. Device fragmentation is calculated to grow by 20% every year.
Here’s an image that shows the Android device fragmentation.
3. Network Connection
Although 5G enabled smartphones are on the rise, the majority of the population are yet to adopt its predecessor, 4G smartphones. This means developers will have to consider the speed differences between 3G, 4G, and 5G smartphones, and ensure the application is capable of working on all networks.
Similarly, developers might also find it challenging to keep the application’s bandwidth usage within a particular limit as carriers, internet service providers (ISPs), or even the operating system may restrict access to the internet beyond certain limits.
4. Increased Number of Device Settings
Smartphones, especially the ones that run Android, are known to allow users to customize them to the core. From placing restrictions on network usage to locking the screen rotation, developers need to be aware of all such settings and how they will affect the application.
Users may toggle on or off those settings anytime while using the app. If testers fail to foresee such device settings and the variations it can cause to the application, they will have little control over how the app will work under such conditions.
5. The Choice Overload With Mobile Testing Tools
There are plenty of automation tools available, and to confidently choose one and avoid the rest can be quite daunting. Although our guide on mobile testing tools will be handy, as a best practice, try weighing the pros and cons of each tool to choose the best.
6. Differences in Battery Capacity
The battery consumption of apps is dependent on computational power, network, and other system resource requirements. As you know, the smartphone market consists of devices with varying storage capacity.
There are smartphones with battery capacities as low as 1000mah and ones with as high as 6000mah. When testing apps, QA testers must be aware of such differences and check how fast the application drains batteries.
For a user having a smartphone with a 6000mah battery, losing 10% of it in 30 mins is no big deal. But if the capacity is just 1000mah, then your app will be deemed to be a battery drainer. Also, the Android OS has introduced an AI-powered feature called Adaptive Battery which will suspend your application if it consumes too many resources in the background.
Common Mobile App Testing Pitfalls to Avoid
1. Testing Mindlessly Without Setting Priorities
Although including diverse scenarios into your testing strategy is useful to make your application flawless, you don’t necessarily need to include all possible scenarios. For example, it is possible that an individual might use your app underwater on a water-proof device.
But it doesn’t mean you have to include such test cases. Otherwise, your testing phase will be incredibly time-consuming and costly. The key is to streamline the testing process by prioritizing the cases. You can also try context-driven testing (testing based on the project and not methodology).
2. Not Giving Importance to UI/UX Testing Earlier On
One of the biggest mistakes developers might make is not giving importance to UI/UX testing from the early stage of development. As the UI and UX are more closely related to the user than the back-end functionality, they must be thoroughly tested for performance and usability.
Testing can be performed as early as in the wireframing phase to ensure that all elements of the app are rightly placed and are intuitive. You can use a prototyping tool (that will mimic how the interactions of elements will take place) to test the app design.
3. Being Unaware of Platform UI/UX Guidelines
Every operating system has a specific set of UI/UX guidelines the developers must follow – for example, Material Design from Google. This will help in creating apps that gel with the OS and includes common design patterns.
If testers are unaware of such guidelines, their efforts will go in vain as the app might get rejected from the App Store or Play Store. Even if you rely on alternative app stores to publish the app, users will have a hard time using the app due to OS incompatibility.
4. Testing Only on Simulators and Emulators
Although simulators and emulators are incredibly cheap as compared to real devices, they are less reliable and can produce results with false positives. Simulators and emulators are reliable only during the initial phase of development.
Even if you have decided to use mobile testing emulators or simulators for the majority of your testing purposes, not testing on real devices will be a naive thing to do. You need to test your app on real devices to understand the look and feel of your app and how users will be experiencing it.
5. Testing Without Knowing What the App Is About
Just like developers and designers, testers must be completely aware of what the app is and what it’s capable of doing. Only then they will be able to write precise test cases.
Knowing the app thoroughly will also help testers understand the sections where a user might get stuck or have difficulty in proceeding.
Although 592 million apps are downloaded every day, 21% of users abandon an application after one use. Of course, relevancy in real-life and how impressive the application is in solving an issue matters – but, its performance, quality and the number of errors a user encounters matter too.
Mobile testing can’t be an afterthought. If you don’t have the right set of resources with enough experience to test an application, you can always outsource your requirements or take the help of freelancers.