HI we've developed a trigger which is fired in the event of deletion upon the ContentDocument object. Wondering if someone could tell me where i am going wrong ! The class is running with no apparent errors however we have 0% code coverage :(  :

My Class : 

@istest
public class count_attach_test {

        static testmethod void attachtest() {
            Account a = new Account();
            a.RecordTypeId='0121r000000pvQm';
            a.name = 'Test NL Account';
            
            
            insert a;
           
        
            Attachment at = new Attachment();
            at.name = 'test attachment';
            at.body = blob.valueof('attachment body');
            at.parentid = a.id;
            insert at;   
            
            
           Opportunity o = New Opportunity ();
           o.RecordTypeId ='0121r000000pvdX';
           o.AccountId =a.Id;
           o.StageName ='Stage 1: Suspect';
           o.Start_Date__c=System.today();
           o.CloseDate=System.today() + 5;
           o.Name='Test NL Opportunity';
           
           insert o; 
           
           o.attachment_edited__c=TRUE;
           update o;            
            
             Attachment at2 = new Attachment();
            at2.name = 'test attachment';
            at2.body = blob.valueof('attachment body');
            at2.parentid = o.id;
            insert at2;   
            
            delete at;
            
            delete at2;
            Blob beforeblob=Blob.valueOf('Unit Test Attachment Body');
ContentVersion cv = new ContentVersion();
        cv.title = 'test content trigger';      
        cv.PathOnClient ='test';           
        cv.VersionData =beforeblob;          
        insert cv;     
            
 ContentVersion testContent = [SELECT id, ContentDocumentId FROM ContentVersion where Id = :cv.Id];
List<ContentDocument> documents = [SELECT Id, Title, LatestPublishedVersionId FROM ContentDocument];

        ContentDocumentLink contentlink=new ContentDocumentLink();
        contentlink.LinkedEntityId=a.id;
        contentlink.ShareType= 'v';
        contentlink.LinkedEntityId = a.Id; 
        contentlink.ContentDocumentId=documents[0].Id;
        contentlink.Visibility = 'AllUsers'; 
        insert contentlink;          
            
            delete contentlink;   
            
            
            //List<Attachment> attachments = [Select Id From Attachment Where parentId = :a.id];
            
           // System.assert(attachments.size() == 1, 'Wrong number of attachments (( ' + attachments.size() );
        }   }

My Trigger :

trigger DeleteFileNL on ContentDocument (before delete) {
                
    Set<id> contentDocumentIDs = new Set<Id>();
    Set<id> sObjectIds = new Set<id>();
    Map<id,Account> tempAccounts = new Map<id,Account>();
    List<Account> accountsToUpdate = new List<Account>();
    
    List<ContentDocument> cdocuments = ( Trigger.isDelete ? Trigger.old : Trigger.new );
    String additonalWhereClause = ( Trigger.isDelete ? 'and ContentDocumentID not in:contentDocumentIDs' : '');
    
    for(ContentDocument cd: cdocuments){
        contentDocumentIDs.add(cd.id);
    }
    
    for ( ContentDocumentLink cdl : [Select LinkedEntityID, ContentDocumentID from ContentDocumentLink where ContentDocumentID IN: contentDocumentIDs]) {
        sObjectIds.add( cdl.LinkedEntityId );
    }
    
    if(sObjectIds.size()>0){
        String query = 'Select LinkedEntityId, count(ContentDocumentID) from ContentDocumentLink where LinkedEntityId in:sObjectIds '+additonalWhereClause+' group by LinkedEntityId';
        AggregateResult[] aggrResult = Database.query(query);
        SYstem.debug(query);
        
        Map<id,Account> accMap = new Map<id,Account>([Select id, name, Attachment_Increment__c from Account where id in:sObjectIds]);
        
        for(AggregateResult ar: aggrResult){
            Object sObjectId = ar.get('LinkedEntityId');
            if(accMap.containsKey((id)sObjectId)){
                Account acc =  accMap.get((id)sObjectId);
                //acc.Attachment_Increment__c = (Integer)ar.get('expr0');    
                acc.Attachment_Increment__c=1*-1;
                acc.Attachment_Edited__c=True;
                System.debug('(Integer)ar.get(expr0)'+(Integer)ar.get('expr0'));
                tempAccounts.put(acc.id,acc);
                accountsToUpdate.add(acc);    
            }
        }
        
        for(Account acc: accMap.values()){
            if(!tempAccounts.containsKey(acc.id)){
                Account a = acc;
            acc.Attachment_Increment__c=1*-1;
               a.Attachment_Edited__c=True;
                accountsToUpdate.add(acc); 
            }
        }
        
        try{
            update accountsToUpdate; 
        }catch(Exception e){
            System.debug('Error Message: '+e.getMessage()+' trace: '+e.getStackTraceString());
        }  
    }
    
}