ElectricSpock and Groovy Android Gradle Plugin: Testing Android with Spock and Robolectric

This project shows how to use the Spock testing framework and Robolectric together for testing Android applications. It also includes a custom Groovy Android Gradle Plugin to make Groovy work in modern Android projects.

Note: This project was inspired by hkhc/electricspock and groovy/groovy-android-gradle-plugin which are already deprecated.

What are Spock and Robolectric?

• Spock: A testing framework for Groovy and Java. It makes your tests easy to read and write. It uses a clear structure: given:, when:, then:.
• Robolectric: A library that lets you run Android tests on your computer (JVM) without an emulator or real device. It simulates the Android environment.

What is ElectricSpock?

ElectricSpock is a library that helps you use Spock and Robolectric together. Normally, they don't work well together because they use different test runners. ElectricSpock solves this problem.

What is the Groovy Android Gradle Plugin?

The Groovy Android Gradle Plugin is a custom plugin that allows you to use Groovy in your Android projects. Apache no longer supports Groovy for Android, but this plugin brings it back!

Why Use This Combination?

• Readable Tests: Spock makes your tests very easy to read and understand.
• Fast Tests: Robolectric makes your tests run very fast because you don't need an emulator.
• Groovy: If you like Groovy, this lets you use it in your Android projects.

How to Use It: A Step-by-Step Guide

Here's how to use ElectricSpock and the Groovy Android Gradle Plugin in your Android project:

Step 1: Apply the Groovy Android Gradle Plugin

First, you need to apply the ru.cusxy.mgga.groovy-android plugin to your module's build.gradle.kts file. This plugin will compile your Groovy code.

plugins {
    id("com.android.application")
    id("org.jetbrains.kotlin.android")
    id("ru.cusxy.mgga.groovy-android") // Apply the Groovy Android plugin
}

Step 2: Add the ElectricSpock Dependency

Next, add the electricspock dependency to your module's build.gradle.kts file. This will add ElectricSpock to your project.

dependencies { 
    testImplementation("ru.cusxy.mgga:electricspock:1.0.0") // Add ElectricSpock
    testImplementation("org.spockframework:spock-core:2.3-groovy-3.0") // Add Spock
    testImplementation("org.robolectric:robolectric:4.14.1" ) // Add Robolectric
    testImplementation("org.codehaus.groovy:groovy-all:3.0.22") // Add Groovy
}

Step 3: Exclude Spock Engine

You need to exclude the default Spock engine from the JUnit Platform. Add this to your build.gradle.kts file:

android {
    testOptions {
        unitTests {
            all { test ->
                test.useJUnitPlatform {
                    excludeEngines("spock") // Exclude the default Spock engine
                }
                test.jvmArgs( // Required for advanced reflection 
                    "--add-opens", "java.base/java.lang=ALL-UNNAMED",
                )
            }
        }
    }
}

Step 4: Create a Groovy Test File

Now, create a Groovy test file in your src/test/groovy directory. For example, WelcomeActivityTest.groovy.

import android.content.Intent
import org.robolectric.RuntimeEnvironment
import spock.lang.Specification
import org.robolectric.Robolectric
import org.robolectric.Shadows
import org.robolectric.android.controller.ActivityController

class WelcomeActivityTest extends Specification {
    
    def "clicking login should start LoginActivity"() {
        given:
            ActivityController<WelcomeActivity> controller = Robolectric.buildActivity(WelcomeActivity)
            controller.setup()
            def activity = controller.get()
        and:
            def expectIntent = new Intent(activity, LoginActivity)
        when:
            activity.findViewById(R.id.login).performClick()
            def actualIntent = Shadows.shadowOf(RuntimeEnvironment.application).getNextStartedActivity()
        then:
            expectIntent.component == actualIntent.component
    }
}

Step 5: Run Your Tests

You can now run your tests from Android Studio or using the Gradle command:

./gradlew :sample:testDebugUnitTest

How It Works: A Simple Explanation

1. Groovy Code: You write your tests in Groovy using Spock's syntax.
2. Groovy Plugin: The ru.cusxy.mgga.groovy-android plugin compiles your Groovy code into Java bytecode.
3. ElectricSpock: ElectricSpock is a custom TestEngine for JUnit Platform. It uses a special trick to load the test classes with Robolectric's class loader.
4. Robolectric: Robolectric simulates the Android environment.
5. Spock: Spock structures your tests and makes them easy to read.
6. JUnit Platform: JUnit Platform runs your tests.

Important Notes

• Groovy is not officially supported by Apache for Android. This project uses a custom plugin to make it work.
• This setup is complex. It's not the standard way to test Android apps.
• Kotlin is the recommended language for Android. Consider using Kotlin and a modern testing framework like Kotest for new projects.
• ElectricSpock is a complex solution. It is not a standard way to integrate Spock and Robolectric.
• This project is for educational purposes. (well almost) It shows how to make Spock and Robolectric work together.

License

This project is licensed under the Apache 2.0.