Mockito 2.x on Android Instrumentation Tests with Kotlin is not working

Hi guys,

I am current working on a Android project using the Kotlin language, and I’m trying mock some classes on Instrumentation Tests. As everything in Kotlin is final by default, we have the known problem of mock final classes, that only works if we apply the “mock-maker-inline” on file “org.mockito.plugins.MockMaker” inside test resources folder (eg.: src/test/resources/mockito-extensions/).

My mockito dependencies on module grade file are:

compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:1.1.2-3"
...

testCompile "junit:junit:4.12"
testCompile "org.jetbrains.kotlin:kotlin-reflect:1.1.2-3"
testCompile "org.mockito:mockito-core:2.8.9”
testCompile ("com.nhaarman:mockito-kotlin:1.4.0", {
    exclude group: 'org.jetbrains.kotlin'
    exclude group: 'org.mockito'
})

androidTestCompile "org.mockito:mockito-android:2.8.9”
androidTestCompile ("com.nhaarman:mockito-kotlin:1.4.0", {
    exclude group: 'org.jetbrains.kotlin'
    exclude group: 'org.mockito'
})
androidTestCompile ("com.android.support.test.espresso:espresso-core:2.2.2", {
    exclude group: 'com.android.support', module: 'support-annotations'
})
androidTestCompile ("com.android.support.test:runner0.5", {
    exclude group: 'com.android.support', module: 'support-annotations'
})
androidTestCompile ("com.android.support.test:rules:0.5", {
    exclude group: 'com.android.support', module: 'support-annotations'
})

For the local unit tests, the “mock-maker-inline” works properly. But for Android Instrumentations Tests it doesn’t works. Reading about it on Mockito documentation, we have:

“Be aware that you cannot use the inline mock maker on Android due to limitations in the Android VM”.

We can’t apply the “mock-maker-inline” for Instrumentation tests.

So, how can we enable Mockito to mock final classes on Android Instrumentations Test ??

[tmurakami]

I think there are two ways.

1. Kotlin all-open plugin
2. DexOpener

Kotlin all-open plugin

This plugin makes classes annotated with a specific annotation open without the open keyword.

First, you put these files into your project:

• app/src/ debug /java/your/app/OpenClass.kt

package your.app

@Target(AnnotationTarget.ANNOTATION_CLASS)
annotation class OpenClass

• app/src/ debug /java/your/app/OpenClassOnDebug.kt

package your.app

@OpenClass
@Target(AnnotationTarget.CLASS)
annotation class OpenClassOnDebug

• app/src/ release /java/your/app/OpenClassOnDebug.kt

package your.app

@Target(AnnotationTarget.CLASS)
annotation class OpenClassOnDebug

Second, configure your app/build.gradle as follows:

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath "org.jetbrains.kotlin:kotlin-allopen:$kotlin_version"
    }
}

apply plugin: 'kotlin-allopen'

allOpen {
    annotation 'your.app.OpenClass'
}

Finally, annotate OpenClassOnDebug to the class you want to mock:

@OpenClassOnDebug
class YourClass

Now you can open classes and members only on debug mode.

DexOpener

This library opens classes and members while testing on Android.

To use this library, configure your app/build.gradle as follows:

android {
    defaultConfig {
        minSdkVersion 16 // 16 or higher
        testInstrumentationRunner 'com.github.tmurakami.dexopener.DexOpenerAndroidJUnitRunner'
    }
}

repositories {
    jcenter()
    maven { url 'https://jitpack.io' }
}

dependencies {
    androidTestCompile 'org.mockito:mockito-android:2.8.9'
    androidTestCompile 'com.github.tmurakami:dexopener:0.9.2'
}

[tmurakami]

I’d like to investigate it, so please file a report in the DexOpener issues.