Google are serious about the global reach of Android. They place translation services front and center in the dev console for Android app publishing. They provide lint checks for localizability and internationalization issues. And they even have a single-line trick for enabling testing your app for localization:
Back in November of 2014, this setting was added under BuildType to tell aapt to inject pseudolocalized text into your build for the following two automatically generated fake locales: en-XA and ar-XB. This is documented in the Android Gradle plugin's DSL here. As you can see, the documentation is a little... "sparse". When I tried it out, it didn't look like it worked at first and I went so far as to open a bug because I couldn't find any directories where the new localized strings files were stored in my project and my app didn't appear to show any of the expected updated strings. It turns out I was wrong in my assumption about how it worked. And my app needs more work ;)
My friend Joe Rogers saw my post about this on Google+ and decided to look into it too but noticed in his app that once he set his device locale to en-XA, the updated strings appeared in an app he is working on so clearly my bug was misguided. So it made us curious where exactly Google's Android SDK team hid these changes. Kids, Android Studio's APK Analyzer is your friend! With it, Joe was able to quickly dig in and discover the strings file with the appropriate pseudolocalization in his APK which was proof positive that the files were dynamically generated during his build. However Google's engineers were clever enough to do this in temporary working files so that the gibberish translations do not end up in your project files and exposed to source control.
For more information about how pseudolocalization works, check out Dan Lew's excellent post here. To keep up with all the changes to the developer tools so that you can use things like this setting, read the release notes for the tools here, and follow all the announcements from Xavier Durochet and his team on Google's Android Developer channel on YouTube and at Google I/O.