Grails test integration service injection

I want to do a full integration test which uses Services that will call other services (I'm using grails 2.4.3). It all works good but when there is an Services within a Service it goes only 2 levels deep and it doesn't go any deeper.

The question is: How can I make the test use all sub-services necessary

class ImportServiceTests extends GroovyTestCase {  

    def grailsApplication
    def fatherService

    def setup() {
    }

    def cleanup() {
    }

    void 'test1'() {
    String a= fatherService.function() // ->subService -> null
}