One of the great new features of Android Studio 2.0 is the automatic implementation of unit testing when you create a new project. However, in it’s base form, it’s only good for testing Java code (nothing Android specific). Mocking an instance of Context won’t do any good if you need it to execute your code.

The solution is…

 Robolectric

The only drawback to this method, is that it doesn’t currently support Api level 22 and above. You will need to adjust the following in your build.gradle…

compileSdkVersion 21
buildToolsVersion "21.1.2"

You will also need to change the version of appcompat you’re using

compile 'com.android.support:appcompat-v7:21.0.0'

Add the following line into the dependencies section

testCompile "org.robolectric:robolectric:3.0"

So all said and done, your build.gradle file should look similar to this

apply plugin: 'com.android.application'

android {
    compileSdkVersion 21
    buildToolsVersion "21.1.2"

    defaultConfig {
        applicationId "net.evanp.umactuallynerdtriviagame"
        minSdkVersion 15
        targetSdkVersion 21
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    testCompile "org.robolectric:robolectric:3.0"
    compile 'com.android.support:appcompat-v7:21.0.0'
}

 

Editing your test classes

Before your class is declared, add the following

@RunWith(RobolectricGradleTestRunner.class)
@Config(constants = BuildConfig.class)

On top of the test method add @test just like usual, but notice how the instance of Context is created

@Test
public void testAbilityToAccessXML() throws Exception {
    Context context = RuntimeEnvironment.application.getApplicationContext();
    ProgramWideFunctions.randomCategory(context);
}

It’s that easy!