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Top 10 Best Practices for Mobile App Testing

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Daniel Knott, author of Hands-On Mobile App Testing, describes 10 best practices required for mobile app testers during the app development lifecycle.
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Mobile phones have been available since the mid-1980s. The devices have changed dramatically over time, but the biggest change (so far) happened in 2007, when Apple presented the first iPhone. Since the premiere of the iPhone, the mobile smartphone market has known only one direction—up! Touch devices are everywhere now, from smartphones to tablets. More than 2 million apps for those devices are available for downloading in the stores of the biggest vendors, and this number continues increasing, with apps for photos, music, games, office productivity, and many more categories. But what about the quality of all those apps? Are the apps reliable, trustworthy, easy to use, well developed, and thoroughly tested?

If you develop apps for use on smart devices, complete and accurate testing needs to be an essential part of your development process. The following 10 best practices will provide you with useful information, techniques, and ideas on how to test a mobile application.

1: Know your customers.

One of the biggest challenges in the mobile app world is high user expectations. Mobile users expect much more from mobile devices and mobile apps than from other applications like those for the Web or desktop. Therefore, knowing your target customers and their expectations is essential. You need information like age, gender, monthly income, mobile usage habits, and geographical location to get a better picture of your customers. This knowledge will help you to understand usage patterns and support mobile testing more appropriately in your business. With thorough understanding of the customer, you can downsize your testing efforts by focusing on what is most important to the user. You may be able to reduce the number of devices for testing, because you only need to test on the devices your customers use.

To get information like this, you can interview customers, conduct market research based on target groups, and use statistics from mobile app stores.

2: Create device groups.

Based on knowledge of the customers, mobile app testers can create mobile device groups, which help to downsize testing efforts in the mobile world. For example, mobile app testers can create groups A, B, and C, with each group having a different priority, such as high, medium, and low. In this example, A has the highest and C the lowest priority. Now the tester adds mobile devices to those mobile device groups based on device usage within each customer target group. For example, group A might contain the latest devices within its target group, whereas group C contains older phones with fewer hardware resources.

Next time a new feature will be developed, the whole team can decide whether this feature must run on all device groups, or only one group. During the testing phase, the mobile app tester can focus on testing only with the devices from the established groups, testing only on those devices specific to customers in each group.

3: Don’t skimp on standard test methods.

Experienced software testers are familiar with software testing terms and techniques such as boundary values, equivalence classes, different coverage types, and acceptance criteria. All this knowledge also applies to mobile testing. Both functional and nonfunctional testing skills from Web or desktop applications are required, with some modifications for mobile testing.

4: Test on various data networks.

Testing in various types of data networks is one of the most important scenarios for testing mobile apps. A mobile app that requires an Internet connection in order to fulfill a task may encounter different data networks while the customer is on the move.

Fast data networks like LTE, 3G, or Wi-Fi differ substantially from slower networks like EDGE or even GPRS. Mobile app testers must be sure that the app works with different network speeds and can handle network transitions; for example, from LTE to EDGE. To test those scenarios, testers must also move around, testing in different network scenarios and with different network carriers.

5: Test in different languages.

If a mobile app is used in different countries, that app very likely will need to support different languages. In that case, mobile app testers must test the app against the various languages it supports. Testing the language is important because every language has different characters and different sizes. For example, the word logout in Figure 1 has a different length and character sets in multiple languages.

Figure 1

Figure 1 Five different versions of a single word.

The word logout is much longer in German and French than in English. In Turkish the expression is two words, and Russian needs a completely different character set. All of these differences can lead to encoding problems. Furthermore, the language can have an impact on your layout. Therefore, it is important to think about languages at the beginning of the development process, to ensure that every UI element is able to handle different languages.

6: Test against all major hardware features.

Mobile devices are packed with powerful hardware and sensors to interact with users and their surroundings. For example:

  • Ambient light sensors
  • Proximity sensors
  • Acceleration sensors
  • Gyroscope sensors
  • Magnetic sensors
  • Pressure, temperature, and humidity sensors
  • Location sensors
  • Touchless sensors

All those sensors can be used within a mobile app. A mobile app tester must understand all the different sensor types and how they are used. If a sensor is used within a mobile app, it is important to test against sensor-specific scenarios, such as different environments or light situations.

In addition to testing your app with the sensors, it is very important to test the mobile app against different hardware features of the device—camera, display, storage, microphone, and so on. All those features can have a huge impact to the mobile app. For example, if the mobile app will take a picture, process it, and upload it to a server, it is important to test this scenario with different cameras from different manufacturers. Every camera with a different lens and resolution will have an impact on picture dimension and size; it is important to test how the mobile app handles the different picture resolutions, sizes, and uploading photos to the server.

7: Thoroughly test for standby, interrupt, and battery issues.

Another very important test is the standby test, in which we check whether the mobile app can handle the standby mode. Testers need to look for UI glitches, data handling, and whether the app maintains state when entering and leaving the standby mode. Furthermore, it is important to test whether the mobile app is updating the last used view when leaving the standby mode. In this case, the app must update the current view in order to get the latest data from a back-end system over the Internet (if this is a use case of the app).

The interrupt test is also very important. A typical mobile device has multiple apps installed, and nearly every app is able to create some sort of notification on the device. Those notifications can have an impact on your app; for instance, while it is processing a picture or sending a file. In order to test this scenario, mobile app testers can use monkey tools, which generate lots of possible interrupts on the device. While the monkey tools are running, testers look for app crashes, freezes, or UI glitches.

While testing the app for standby and interrupt scenarios, mobile app testers must keep an eye on battery consumption. Recommended: Start every testing activity with a fully charged battery, and then note the battery state every 10 minutes in order to get an impression of battery drain. Also, test the mobile app with a remaining device battery charge of 10–15%, because most devices will enter a battery-safe mode, disabling some hardware features of the device. In this state, it is very likely to find bugs such as requiring a turned-off hardware feature (GPS, for example).

With the help of tools, you can perform both interrupt and standby testing.

8: Test updates and install/uninstall procedures.

Before submitting a mobile app to an app store, testers need to test the app’s update and installation processes. Every major mobile platform offers tools to test the update process, in order to simulate updating from an older app version to the latest one. In this test scenario, a previously logged-in user must not be logged out after the update, or the user’s database changes will have no impact on the existing data on the phone.

During the install and uninstall tests, mobile app testers must look for crashes or any other problems that might occur. After the app is uninstalled, check the device storage to make sure that the app data has been completely removed.

9: Test usability in multiple ways.

Throughout the complete mobile app development and testing lifecycle, it is very important to check usability. Mobile users have very high expectations for the usability of their apps. All UI elements must be easy to use and understand, and the app must provide clear explanatory text and error messages. In error situations, the app must guide the user in how to solve the current problem in the app.

Mobile app testers must be familiar with the different usability platform guidelines, to verify that their apps meet all guidelines. A very good approach to testing the usability of an app is to ask customers about it directly. Invite them to a usability lab and ask specific questions about new features; or provide customers with early versions of new features to see whether users are able to work comfortably with the app, and make sure that every feature is easy to understand.

It is also possible to perform some ad hoc usability testing with possible customers; for example, in an Internet café.

10: Restrict permissions and check all log files.

The last point in suggested best practices for mobile app testing deals with app permissions and log files. During the development and testing phase, mobile app testers need to verify that the app is using only the permissions that the app requires, and no more. Mobile users are very sensitive about their private data and most likely will not install or use an app with unclear permission requirements. For example, when the app requires only the camera and an Internet connection, it makes no sense to require permissions for the calendar, SMS, or personal identification.

In another test scenario, mobile app testers need to connect the mobile device to a computer to check the log files, looking for errors, stack traces, warnings, and any kind of information that is not allowed to be there. Furthermore, it is very important to check the log level before submitting the app to the app store. The log level must be set to release mode, to avoid showing too much app information to other people.

Wrapping Up

For more mobile testing scenarios and ideas, as well as information about mobile test automation tools and a mobile test strategy, check out my book Hands-On Mobile App Testing.

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