// inside android block
    debug {
        shrinkResources true  // removes unused graphics etc
        minifyEnabled true
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        testProguardFile('test-proguard-rules.pro')
    }

# Proguard rules that are applied to your test apk/code.
-ignorewarnings

-keepattributes *Annotation*

-dontnote junit.framework.**
-dontnote junit.runner.**

-dontwarn android.test.**
-dontwarn android.support.test.**
-dontwarn org.junit.**
-dontwarn org.hamcrest.**
-dontwarn com.squareup.javawriter.JavaWriter
# Uncomment this if you use Mockito
#-dontwarn org.mockito.**
The add the following to your build.gradle for your app. To use the proguard file when testing.

/project/app/build.gradle

android {
    debug {
        minifyEnabled true
        testProguardFile 'proguard-test-rules.pro'
    }
}

android {
    variantFilter { variant ->
        if (variant.buildType.name.equals('debug')) {
            variant.setIgnore(true);
        }
    }
}

buildscript {
    ext.kotlin_version = '1.2.10'

    ...

    dependencies {
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}
apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'

repositories {
    mavenCentral()
}

dependencies {
    compile "org.jetbrains.kotlin:kotlin-stdlib"
}

compile "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"

configurations.all {
    resolutionStrategy {
        force "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    }
}

// Instead, because the new build model delays dependency resolution, you
// should query and modify the resolution strategy using the Variant API:
android {
    applicationVariants.all { variant ->
        variant.getCompileConfiguration().resolutionStrategy {
            ...
        }
        variant.runtimeConfiguration.resolutionStrategy {
            ...
        }
        variant.getAnnotationProcessorConfiguration().resolutionStrategy {
            ...
        }
    }
}

android.testVariants.all { variant ->
    variant.getCompileConfiguration().exclude group: 'com.jakewharton.threetenabp', module: 'threetenabp'
    variant.getRuntimeConfiguration().exclude group: 'com.jakewharton.threetenabp', module: 'threetenabp'
}

compile "org.jetbrains.kotlin:kotlin-stdlib-jdk7"
compile "org.jetbrains.kotlin:kotlin-stdlib-jdk8"

compile "org.jetbrains.kotlin:kotlin-reflect"
testCompile "org.jetbrains.kotlin:kotlin-test"
testCompile "org.jetbrains.kotlin:kotlin-test-junit"

apply plugin: 'kotlin-kapt'