Gradle: packaging fat jar with tests

task testsJar(type: Jar) {
    from sourceSets.test.output
}

task fatJarWithTests(type: Jar) {
    manifest {
        attributes 'Main-Class' : 'com.example.Main'
    }
    baseName = project.name + '-all'
    from {
        configurations.compile
                .collect {
            it.isDirectory() ? it : zipTree(it)
        }
    }
    with jar, testsJar
}