Grails inject services into domains during unit tests 2.4.x

Here is the domain class which contains a simple springSecurityService

class Login {

  def springSecurityService

  String username
  String password

  boolean enabled;
  boolean accountExpired;
  boolean accountLocked;
  boolean passwordExpired;

  static constraints = {
    username blank: false, unique: true
    password blank: false
  }

  def beforeInsert() {
    encodePassword()
  }

  def beforeUpdate() {
    if (isDirty('password')) {
        encodePassword()
    }
  }

  protected void encodePassword() {
    password = springSecurityService.encodePassword(password)
  }

}

Simple Unit Spec

import grails.plugin.springsecurity.SpringSecurityService
import grails.test.mixin.TestFor
import grails.test.mixin.TestMixin
import grails.test.mixin.support.GrailsUnitTestMixin
import spock.lang.Specification

@TestFor(Login)
@TestMixin(GrailsUnitTestMixin)
class LoginSpec extends Specification {

  def setup() {
    defineBeans {
        springSecurityService(SpringSecurityService)
    }
  }

  def cleanup() {
  }

  void "test service injected in domain"() {
    given:''

    when:''
    Login l = new Login()


    then:''
    applicationContext.getBean("springSecurityService") != null
    // fails
    l.springSecurityService != null
  }
}

I wanted to test a simple Login.save(), but realized that springSecurityService isn't getting injected, so wanted to understand the best way to inject a service into a domain object for unit tests.

any thoughts, suggestions ?