MyService2Spec.groovy

void "starting jobs creates threads"() {
  when:
  myService.startJobs()
  Thread.sleep(300)
  then:
  Thread.getAllStackTraces().keySet().findAll \\
    {Thread thread -> thread.name.contains "Job"}.size() > 1
  cleanup:
  myService.endJobs() //important, or you risk threads contaminating your next test. (happened to me)
}