Stubbing Spock Specification

MySpec.groovy

import spock.lang.*

class MySpec extends Specification {

  def "should size list return always 3"() {
    given:
      List list = Stub()
      list.size() >> 3

    expect:
      list.size() == 3
  }

  def "should thrown exception when calling size list"() {
    given:
      List list = Stub()
      list.size() >> { throw new IllegalStateException() }

    when:
      list.size()

    then:
      thrown(IllegalStateException)
  }
}