build.gradle

buildscript {
  ext.kotlin_version = '1.3.11'
  ext.junitVersion = '5.3.2'

  repositories {
    mavenCentral()
  }
  dependencies {
    classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
  }
}

apply plugin: 'kotlin'
apply plugin: 'application'

mainClassName = 'demo.HelloWorldKt'

defaultTasks 'run'
test { useJUnitPlatform() }

repositories {
  mavenCentral()
}

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

  testCompile "org.mockito:mockito-core:2.23.0"
  testCompile "org.assertj:assertj-core:3.11.1"
  testCompile "org.junit.jupiter:junit-jupiter-api:$junitVersion"
  testCompile "org.junit.jupiter:junit-jupiter-params:$junitVersion"
  runtime "org.junit.jupiter:junit-jupiter-engine:$junitVersion"
  testCompile "org.jetbrains.kotlin:kotlin-test-junit:$kotlin_version"
}

jar {
  manifest { attributes 'Main-Class': 'demo.HelloWorldKt' }
  from { configurations.compile.collect { it.isDirectory() ? it : zipTree(it) } }
}