public interface CustomDao {
    List<Integer> getIds()
    ModelObject getModelById(int id)
}

class ModelObject {
    int id
}


class CustomServiceUtil {
    CustomDao customDao

    public List<Object> createOutputSet() {
        List<ModelObject> models = new ArrayList<ModelObject>();
        List<Integer> ids = customDao.getIds();
        for (Integer id in ids) {
            models.add(customDao.getModelById(id));
        }
        return models
    }
}

class TestSpec extends Specification {

    def 'crazy closures'() {
        def mockDao = Mock(CustomDao)
        def idSet = [9,10]

        given: 'An initialized object'
        def customService = new CustomServiceUtil()
        customService.customDao = mockDao

        when: 'createOutput is called'
        def outputSet = customService.createOutputSet()

        then: 'the following methods should be called'
        1*mockDao.getIds() >> {
            return idSet
        }

        idSet.each {
            mockDao.getModelById(it) >> {int id ->
                def tmp = new ModelObject()
                println "Inside stubbed closure with value of id as $id"
                tmp.id = id
                return tmp
            }
        }

        and: 'each compute package is accurate'
        2 == outputSet.size()
        9 == outputSet.get(0).getId()
        10 == outputSet.get(1).getId()
    }
}

//Prints
Inside stubbed closure with value of id as 9
Inside stubbed closure with value of id as 10