The Ins & Outs of Mobile App Testing

Over the last decade, application testing has continually proved itself to be an important concern. When done well, testing can drastically reduce the number of bugs that make it into your release code (and thus actually affect your users). In addition, good testing approaches will help your team catch bugs earlier in the development lifecycle – resulting in a savings of both time and money (not to mention reputation with your users). Code that has good test coverage enables you and your team to make changes and introduce new features to your app without the fear of it breaking existing functionality.


The word “Testing” is a large umbrella, and is usually better understood when you break it down to specific types of testing. For example:

  • Unit Testing – automated tests written by developers, with each test targeting a narrow slice of application behavior.
  • Functional & Acceptance Testing – typically performed by QA personnel or automated UI testing frameworks.
  • Performance Testing – often performed manually with profiling tools (for example – heap and CPU profiling tools), though many mobile app developers are moving towards integrating app analytics to gather this data from real usage as well.

That’s certainly not an exhaustive list of the types of testing, but enough to make an important point: [tweetable]mobile applications face several challenges when it comes to testing[/tweetable]. Key among those challenges are:

  • Platform & Device Diversity
  • Immature Tooling
  • Lack of Awareness

If you opt to write native applications for each target platform, then any code-level testing (i.e. – Unit Tests) will not be transportable as you move from Objective-C (iOS) to Java (Android). In addition, any scripted UI-Automation testing tools may not work for multiple platforms (or at the very least require separate scripts for each platform). Hybrid solutions like PhoneGap, or cross-compiled solutions like Xamarin can offer a single approach to unit testing (given a single codebase for multiple platforms) – but do not always offer the same level of quality as native tooling when it comes to performance profiling. Despite the trade offs involved, I’ve found in my own experience that [tweetable]the biggest barrier to entry in mobile app testing is often a lack of awareness of what tools are available[/tweetable]. That is the barrier which I hope to address in this post.

Unit Testing

Unit testing for specific platforms or cross-platform tools is not difficult, and your options abound. Let’s look at a sample of some of these choices.


iOS developers who’ve been writing Objective-C for a while may be familiar with OCUnit, which shipped with XCode prior to the XCTest framework. It’s still supported in XCode 5, but the understanding is that new and future projects should focus on using XCTest.

Don’t let Apple’s sparse documentation on unit testing deter you from checking out the XCTest framework. If you’re running an OS X Server, you can also take advantage of the XCode service’s continuous integration features. As part of a continuous integration workflow, you can create “bots”, which can continually build and test your app.

Many developers prefer a Behavior-Driven-Development (BDD) style syntax for unit testing. If this describes you, be sure to check out Kiwi – a BDD style unit testing framework for iOS.

One other important mention is OCMock a mocking framework for iOS. Mocks are an indispensable part of writing adequate tests around your application’s behavior.


JUnit is perhaps by far the most well known (and officially recommended by Google) testing framework for Android. The JUnit Android extensions allow you to mock Android components, but I’ve also seen quite a number of Android developers use JUnit with Mockito, another Android mocking framework.

Robolectric takes a different – and very interesting – approach by allowing you to run your Android unit tests in the normal JVM (Java Virtual Machine), without the need for an emulator. This enables your tests to not only run from within your IDE, but also as part of a continuous integration workflow.


Qt made the top 5 most used CPTs in 2013. If you’re building mobile applications with Qt, you’ll be happy to know about QTestLib, a unit testing framework built by Nokia. Based on my research, it appears that QTestLib can be integrated with a 3rd party continuous integration workflow – enabling very helpful testing automation.

PhoneGap/Apache Cordova

Web-based hybrid approaches to mobile apps can take advantage of a host of testing and mocking frameworks, not to mention scripted UI/acceptance testing tools as well (more on that in a moment). When it comes to unit testing JavaScript, three of the biggest names are QUnit, Mocha and Jasmine. I’ve personally used all three, with my favorite setup including Mocha and expect.js (which provides a BDD style test syntax). Mocking and “spy” frameworks abound in JavaScript as well, with Sinon.js and JsMockito among the more popular stand-alone mocking options.

Many PhoneGap developers take advantage of tools like PhantomJS – which is a “headless” (no UI) WebKit browser, with a JavaScript API. PhantomJS can be easily integrated into a continuous integration workflow to automatically run unit tests against your hybrid mobile application’s codebase.


Xamarin uses a customized version of NUnit (ported from JUnit), called NUnitLite which enables you to write unit tests against your Xamarin iOS & Android projects. For any shared codebase, you can use the unit testing framework of your choice.

Scripted UI Testing

Not every team can afford to hire an army of manual QA testers, despite how valuable that can be. Automated tooling can bridge the gap.

If you’re writing native iOS and Android apps, you’re in luck. Apple provides an “Automation instrument” that will automate UI tests against your iOS mobile application. The Android SDK provides the “uiautomator” library, described as “A Java library containing APIs to create customized functional UI tests, and an execution engine to automate and run the tests.” In addition to these, you can use third party tools like Squish, Ranorex and Perfecto Mobile’s MobileCloud Automation to automate UI tests against Android and iOS apps, web apps and more. It’s worth mentioning that Perfecto Mobile’s MobileCloud Automation exposes an API to better facilitate integration with existing build/continuous integration tools. Perfecto Mobile also offers MobileCloud Interactive, which enables you to “perform remote manual testing on real smartphones and tablets regardless of where you are” – who wouldn’t want to have a “testing army” of real mobile device users at their disposal?

Among the more interesting developments in mobile UI automated testing is the emergence of an open source project named Appium. Appium uses the WebDriver JsonWireProtocol to interact with iOS, Android and Firefox OS apps and gives you the choice of writing your UI tests in any WebDriver-compatible language (Java, Objective-C, JavaScript, PHP, Python, Ruby, C#, Clojure, Perl and others).

Performance & Profiling

Apple’s Instruments is one of the more impressive native toolsets I’ve seen recently. With Instruments, it’s possible to profile how your app executes, run stress tests, record and replay user actions, create custom instruments and a lot more. If you’re writing native iOS apps & not using Instruments, I recommend reading through the Quick Start to get up to speed.

With Android apps, you have several (albeit, lower-level) tools available: Systrace & Traceview. You can also use the Device Monitor to view memory usage based on logcat messages.

For hybrid mobile apps, you have a host of mature desktop browser tools (Chrome Developer Tools, Firefox/Firebug, etc.), which you can bring to bear on your app to profile CPU usage, memory, DOM manipulation and much more.

Many mobile developers have started taking advantage of third party analytics services such as Google Mobile Analytics, Countly, EQATEC, Flurry, Perfecto Mobile’s MobileCloud Monitoring and many others. The focus of these kind of analytics is usually more about how your app is actually used, user engagement, demographics, feature popularity, etc. However, it provides an opportunity to measure certain pieces of application performance from within real-world usage. While I wouldn’t recommend this being your first line-of-defense in performance testing, having the ability to track real world performance metrics can be a powerful tool in tuning your application to your users’ needs.

We’ve only scratched the surface of the various testing options available for mobile app development. What testing approaches & tools are you using when writing mobile apps? If you’re not currently testing your application, what are some factors that would change your mind?

– Jim (ifandelse)

Business Community Tips

Test Early, Test Often, Test on Everything?

Testing any mobile app presents a wide range of challenges. The often repeated but rarely followed software best practice of test early, test often is harder to adhere to than usual due to the fragmentation of the target environment and the relative maturity of tools. The increased acceptance of apps by mainstream consumers and intense competition have raised the bars for user experience and quality. There is more to test than ever, yet often very limited budget for doing so. Fortunately every challenge presents an opportunity and a vast array of tools vendors are racing to fill the gaps.

What to test?

Much of the traditional software testing literature focuses on various forms of functional testing – ensuring the system does what it’s meant to do. With a strong trend towards simpler, single purpose apps, this is often the easiest thing to verify in a mobile app project. There is now a much stronger focus on the user experience and this requires testing of an entirely different nature. The most effective way to test that an app is easy (or even fun) to use is to get feedback from real users. Doing that and finding major issues after the app has been built is a very expensive mistake to make, so most developers and designers will want to create mock-ups or prototypes for early feedback. There’s a wide range of tools to help with this task from simple wireframing through to full interactive prototyping. Given the importance of animations within mobile apps to enable users to discover interface interactions and learn to navigate, more complete prototypes are becoming increasingly desirable. As users become more sophisticated and specialist tools reduce the time and effort required to create interactive prototypes this trend is likely to continue.

With the majority of app store revenues coming through in-app purchases, another more specialized form of testing the design of an app is becoming increasingly important – split testing. On the desktop web, tools for trying out design and copy variants to optimize sites for specific user behaviours are very mature and the best of them can be used by staff with no development skills. In the mobile world most of the tools in this space are still very immature and developer-focussed. The responsive design trend on the web and the more restricted deployment options for native apps make this a more challenging problem for mobile devices but we expect the tools in this sector to mature rapidly.

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When to test?

The earlier you find problems with software, the cheaper it is to fix them. As such, it makes sense to start testing as early as possible. How about testing the idea for the app via a mobile market research service before you even create your first wireframes? It’s worth considering – if you can’t generate interest in your app idea with a simple pitch it’s not going to be easy to get people to download it from the store either.

For most apps (particularly native apps) it’ll be worth using one of the mock-up or prototyping tools mentioned above and test the design before you start coding the real app. It’s much cheaper to iterate a simple design prototype than a native app. However, you’ll still want to try out the actual app with real users before you launch it. To help with that there’s a range of beta testing services that can help you distribute your beta app and find and/or manage testers. There are also services to help you get feedback from your users before and after the app launches. Providing a highly accessible feedback channel for users in the app is your best hope for preventing the inevitable disgruntled few from leaving bad reviews.

Ideally an app will be developed and tested iteratively with functional testing of new features and full regression tests for the existing functionality run for each iteration. This level of testing can get extremely expensive and time consuming unless it is automated. Fortunately there are several tools, open source frameworks and third party services that can help out there too.

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Where to test?

Another major problem for mobile developers is the scale and fragmentation of the market they’re trying to serve. Collecting a full library of test devices with major firmware variants is way beyond the budget of most developers, let alone the effort that would be required to test manually on all of them. Automated testing solutions can help here also and some services provide access to a large set of devices for remote testing too. However, it’s simply not feasible for most developers to test every version of their apps on all the device and firmware combinations they support. This limitation means some bugs are almost guaranteed to escape into the wild; the important thing then becomes how quickly you discover and fix them. For this reason, crash analytics and bug tracking tools are becoming increasingly important. Another useful weapon in this battle is your usage analytics data – it can enable you to focus testing on the devices which are most popular amongst your user base and also spot changes in use on particular device models that might signal a non-fatal error that’s causing users to abandon the app.

Finally, for some apps, where they are tested geographically may also be important. Do you know what the performance of your app is like for users who are far from your servers? If you use SMS, do you know how long it takes to get to users on different networks around the world (or if it even gets there). Have the localisations for your app been tested by native speakers? Our automated testing and app certification sectors include companies that can crowdsource beta testers or provide access software testing professionals almost anywhere in the world to help you scale globally without leaving your desk.

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