Learning Android Gradle Unit Testing


The Gradle build system is pretty robust and it is becoming mainstream. That means it behooves you to start putting it to use. I’d been spending a little time with various Gradle based projects and realized that there were a couple of things missing… documentation on the Android plugin. Sure you can look here but I’m a rebel and I like to pretend there isn’t any documentation while learning the hard way. Hi, I’m Cliff. You’re here because you don’t read documentation. I’m here to show you how to reverse engineer your own documentation using Gradle/Groovy goodness. Today’s article is going to be short since it only covers a small area.

So I’m playing with a Gradle based Android project trying to get unit testing to work when I hit a snag. I had been so used to Maven and following all of the popular Gradle documentation online will have you believing, “Hey this works mostly like Maven!” In fact, a basic Java Gradle project is mostly indistinguishable from a Java Maven project from the outset in that they both follow the same familiar structure. Just drop your compile files into “src/main/java” and your test stuff into “src/main/test”. You hardly have to write any code in your build file to work with these types of projects. So it is almost a given that I get lost when I opened my new Gradle-based Android project and tried to add unit tests. Let’s start from my first sign of trouble in Android Studio. My initial step was to create a test folder for my project to begin adding tests to. Doing so I noticed it was colored manilla-tan and not green as I’d expected. Now in IntelliJ there’s a nice little right-mouse context menu that allows you to mark a folder as either a source directory, a test directory or a resource directory. Right clicking in Andoird Studio did not reveal the same feature so I thought there was a bug in the recent Canary update. (“Doggone Canary bleeding edge!”, is what I murmured to myself in disgust.) Then I thought I could just edit my Gradle build file to get the proper color on my folder allowing me to right click tests and run them directly.

I copied a source set config from an earlier Ant-based Android project that I coerced into Gradle. In this project I used the sourceSet configs to map the legacy Android-Ant structure into something Gradle could work with. This was done many months ago and several changes to Gradle and Android has happened since then but I figured it would still work the same since the original project was still functional. Dropping the following under the android config in my build.gradle did not change the color:

sourceSets {
    test {
        java.srcDirs = ['src/test/java']
    }
}

Out of frustration I poured through all the Gradle documentation I had. Unfortunately I was reading Gradle docs and not Android plug docs for Gradle so I was confused into thinking what I was doing should work. Just before complaining on StackOverflow or filing a bug report I found a little hack I could use to debug my build.gradle. Remembering that a Gradle build is just Groovy source code gave me relief as I could just drop a println anywhere and inspect build elements in my console. (I use the terminal plugin in Android Studio so I didn’t even have to leave myIDE to try it.) I looked up the SourceSet API and then coded the following:

android.sourceSets.each {
    println "Sourceset: ${it.name} java source: ${(it.java ? it.java.srcDirs.join(':'):'Null')}"
}

That’s when it became apparent that there is not test source set in the Android plugin, only an androidTest sourceSet! I also learned, as I had figured, that there was no need to code an explicit source set so long as I followed whatever the convention was. I finally decided to write this blog post out of frustration because NOWHERE IN THE INTERNET UNIVERSE IS THERE ANY DOCUMENTATION EXPLAINING WHERE ANDROID TEST SOURCE LIVES!!! HOw frustrating it is to be an Android developer these days!

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