How can I test this class in Salesforce?

I am creating a new Content Link on Service Appointment inserting from the parent work order and I am struggling on how I would write a test against this.

trigger LinkWorkOrderContentToServiceAppointment on ServiceAppointment (after insert) {

List<ContentDocumentLink> CDLtoUpdate = new List<ContentDocumentLink>();
Set<ID> TicketIDs = new Set<ID>();

for (ServiceAppointment SA : Trigger.new) {
TicketIDs.add(SA.Master_Ticket__c);
}

List<ContentDocumentLink> ContentDocumentLinks = new List<ContentDocumentLink>([select id,ContentDocumentId,LinkedEntityId from ContentDocumentLink where LinkedEntityId in:TicketIDs]);

for (ContentDocumentLink CDL : ContentDocumentLinks){
for (ServiceAppointment SA : Trigger.new){
if(CDL.LinkedEntityId == SA.Master_Ticket__c){
if(CDLtoUpdate.size()>199){
insert CDLtoUpdate;
CDLtoUpdate.clear();
}
ContentDocumentLink NCDL = new ContentDocumentLink(ContentDocumentId = CDL.ContentDocumentId, LinkedEntityId = SA.Id, ShareType ='V', Visibility = 'AllUsers');
CDLtoUpdate.add(NCDL);
}
}
}
if(CDLtoUpdate.size() > 0){
insert CDLtoUpdate;
CDLtoUpdate.clear();
}

}