How can I access an inner Enum in Grails Test?

I have a Groovy domain like this:

package fantasy

    class Notification {

        enum NotificationType {
            INVITE_GENERAL, INVITE_CONTEST
        }

        NotificationType type

        String emailTo
        User toUser
        User fromUser
        String message
        boolean wasReadByToUser
        boolean wasReadByFromUser
        boolean fromUserRemoved

        Date dateCreated

        static constraints = {
            type(blank: false)
            toUser(nullable: true)
            emailTo(email: true, blank: false)
        }

        static mapping = {
            autoTimestamp true
        }
    }

And I need to access a notification type in a Grails.Groovy/Spock test...

How can I get at the Enum, as I've tried just about everything I can do. Here is my test so far:

package fantasy

import grails.test.mixin.TestFor
import spock.lang.Specification

/**
 * See the API for {@link grails.test.mixin.domain.DomainClassUnitTestMixin} for usage instructions
 */
@TestFor(Notification)
@Mock([Notification, User])
class NotificationSpec extends Specification {


    // Notification
    Notification notification 
    // *** Here is my issue *** //
    Notification.NotificationType type = Notification.NotificationType.INVITE_CONTEST

    // Fields
    String emailTo = "fmulder@fox.com"
    String message = "Trust No One"
    boolean wasReadByUser = false
    boolean wasReadByFromUser = false
    boolean fromUserRemoved = false

    // Date
    Date dateCreated

    // Mocks
    def toUser
    def fromUser

    def setup() {
        toUser = Mock(User)
        fromUser = Mock(User)
        dateCreated = new Date()

    }

    def cleanup() {
        toUser = null
        fromUser = null
        dateCreated = null
    }

    void "test valid entry will validate"() {
        setup:
        notification = new Notification(
            type: type,
            emailTo: "danaScully@fox.com",
            toUser: toUser,
            fromUser: fromUser,
            message: message,
            wasReadByUser: false,
            wasReadByFromUser: false,
            fromUserRemoved: false,
            dateCreated: dateCreated
        ).save(failOnError: false, flush: true)
        expect:
        Notification.count() == 1
        notification.validate()
    }

}

How can I access that inner Enum?