Gradle pieces needed for robolectric integration in Android Studio

important gradle pieces

task robolectric(type: Test, dependsOn: assembleRelease) {

    testClassesDir = sourceSets.robolectric.output.classesDir

    android.sourceSets.main.java.srcDirs.each { dir ->

        project.getPlugins().getPlugin('android').prepareTaskMap.each {
            sourceSets.robolectric.compileClasspath += files(it.value.explodedDir.getAbsolutePath() + '/classes.jar')
            sourceSets.robolectric.runtimeClasspath += files(it.value.explodedDir.getAbsolutePath() + '/classes.jar')
        }

        def buildDir = dir.getAbsolutePath().split('/')
        buildDir = (buildDir[0..(buildDir.length - 2)] + ['build', 'classes', 'release']).join('/')

        sourceSets.robolectric.compileClasspath += files(buildDir)
        sourceSets.robolectric.runtimeClasspath += files(buildDir)
    }

    classpath = sourceSets.robolectric.runtimeClasspath
}

android {
  sourceSets {
        main {
            manifest.srcFile 'AndroidManifest.xml'
            java.srcDirs = ['src']
            resources.srcDirs = ['src']
            aidl.srcDirs = ['src']
            renderscript.srcDirs = ['src']
            res.srcDirs = ['res']
            assets.srcDirs = ['assets']

        }
        androidTest {
            java.srcDirs = ['test']
        }
    }
}

dependencies {
    androidTestCompile 'org.robolectric:robolectric:2.2'
    androidTestCompile 'org.mockito:mockito-all:1.9.5'
    androidTestCompile group: 'junit', name: 'junit', version: '4.+'
    androidTestCompile 'com.google.android:android:4.0.1.2'
    androidTestCompile files('test-libs/google-play-services.jar')
    androidTestCompile ('com.android.support:support-v4:18.0.0')
}