Enable groovy for unit test of android project with other jvm language in gradle

build.gradle

dependencies {
    testCompile "org.spockframework:spock-core:1.0-groovy-2.4"
    testCompile "cglib:cglib-nodep:3.1"
    testCompile "org.objenesis:objenesis:2.1"
}

android.applicationVariants.all {
    def variantName = it.name
    def capitalizedName = "${variantName[0].toUpperCase()}${variantName[1..-1]}"

    def compileUnitTestJavaWithJavac = tasks.findByName("compile${capitalizedName}UnitTestJavaWithJavac")

    def compileUnitTestGroovy = tasks.create(name: "compile${capitalizedName}UnitTestGroovy", type: GroovyCompile) {
            source("src/test/java", "src/test/groovy")
            include('**/*.groovy')
            destinationDir  = compileUnitTestJavaWithJavac.destinationDir
            classpath       = compileUnitTestJavaWithJavac.classpath
            groovyClasspath = compileUnitTestJavaWithJavac.classpath
    }
    compileUnitTestJavaWithJavac.dependsOn(compileUnitTestGroovy)
}