Mock and Spy in Spock Specification

MySpec.groovy

import spock.lang.*

class MySpec extends Specification {
  
  def starshipName = 'NCC-1701'

  def "size method should be executed three times"() {
    given:
        List list = Mock()
    when:
        list.add(1)
        list.add 2
        list << 3
    then:
        0 * list.add(!null)
        3 * list.add(_ as Integer)
  }

  def "should taking off starship and print text to console"() {
    given:
        Launchable launchable = Stub()
        OffService service = Spy(USSEnterprise, constructorArgs: [launchable])
    when:
        service.takeOff(new Starship(name: 'NCC-1701'))
    then:
        1 * service.takeOff({ it.name == starshipName })
  }
}

Services.groovy

interface Launchable { }
 
interface OffService {
    void takeOff(Starship starship)
}

class Starship {
  String name
}
 
class USSEnterprise implements OffService {
 
    USSEnterprise(Launchable launchable) { }
 
    @Override
    void takeOff(Starship starship) {
        println "${starship.name} taking off..."
    }
}