You can open this sample inside an IDE using the IntelliJ native importer or Eclipse Buildship.

This sample shows how to test Groovy projects using the Spock Framework with Gradle.

For applications:

application/build.gradle
plugins {
    id 'groovy'
    id 'application'
}

dependencies {
    implementation project(':list')
    implementation project(':utilities')
    implementation 'org.codehaus.groovy:groovy-all:2.5.7'
    testImplementation 'org.spockframework:spock-core:1.3-groovy-2.5'
}

application {
    mainClass = 'org.gradle.sample.app.Main'
}
application/build.gradle.kts
plugins {
    groovy
    application
}

dependencies {
    implementation(project(":list"))
    implementation(project(":utilities"))
    implementation("org.codehaus.groovy:groovy-all:2.5.7")
    testImplementation("org.spockframework:spock-core:1.3-groovy-2.5")
}

application {
    mainClass.set("org.gradle.sample.app.Main")
}

For libraries:

list/build.gradle
plugins {
    id 'groovy'
}

dependencies {
    implementation 'org.codehaus.groovy:groovy-all:2.5.7'
    testImplementation 'org.spockframework:spock-core:1.3-groovy-2.5'
}
list/build.gradle.kts
plugins {
    groovy
}

dependencies {
    implementation("org.codehaus.groovy:groovy-all:2.5.7")
    testImplementation("org.spockframework:spock-core:1.3-groovy-2.5")
}

Running the tests:

$ ./gradlew test

> Task :application:test
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.codehaus.groovy.vmplugin.v7.Java7$1 (file:/Users/daniel/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy/2.5.7/99907efe4b69f800c42584386f5d668e4d952bd5/groovy-2.5.7.jar) to constructor java.lang.invoke.MethodHandles$Lookup(java.lang.Class,int)
WARNING: Please consider reporting this to the maintainers of org.codehaus.groovy.vmplugin.v7.Java7$1
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

> Task :library:test
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.codehaus.groovy.vmplugin.v7.Java7$1 (file:/Users/daniel/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy/2.5.7/99907efe4b69f800c42584386f5d668e4d952bd5/groovy-2.5.7.jar) to constructor java.lang.invoke.MethodHandles$Lookup(java.lang.Class,int)
WARNING: Please consider reporting this to the maintainers of org.codehaus.groovy.vmplugin.v7.Java7$1
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

BUILD SUCCESSFUL
7 actionable tasks: 7 executed

For more information, see Testing in JVM project chapter.

You can also generate this project locally using gradle init.