Hi,
I have 2 triggers:
1.Contentdocument 2.Contentdocumentlink
which counts the no of attachments attached in lightning and roll it up to parent object.But i have an issue in test class coverage.
It shows:Insert failed. First exception on row 0; first error: CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY, FilesRollupCount: execution of AfterInsert caused by: System.QueryException: Implementation restriction: ContentDocumentLink requires a filter by a single Id on C
please help me with this.Thanks in advance.
Below is  my test class:

@isTest

public class ContentDocTrigger_Test{
    private static Account dis1;
    
    static testmethod void method_1(){
        
        dis1 = Initial_Test_Data.createAccount('test Account1','Distributor');
        dis1.Contact_Number_Mobile__c ='7259582222'; 
        dis1.Party_Type__c = 'Distributor';
        dis1.Status__c = 'Existing';
        dis1.Ramco_ID__c = 'abc123';
        insert dis1;
        
        Promotion__c prm = new Promotion__c();            
        prm.Date__c=System.today();
        prm.Type__c='Dealers Meet';
        prm.Total_Expenses__c = 1000;
        prm.Total_no_of_attendees__c = 0;
        prm.State__c = 'Karnataka';
        prm.Location__c = 'BTM';
        prm.Distributor__c=dis1.id;
        insert prm;        
        system.assert(prm.id != null);
        
        ContentVersion cver = new ContentVersion();
        cver.ContentLocation = 'S';
        cver.VersionData = Blob.valueOf('Unit Test Attachment Body');
        cver.PathOnClient = 'Retailer.png';
        cver.Title = 'Retailer Image';
        insert cver;       
        
        
        ContentVersion testContent = [SELECT id, ContentDocumentId FROM ContentVersion where Id = :cver.Id];
        Promotion__c promo = [select id from Promotion__c where id=:prm.id];
        //create ContentDocumentLink  record 
        ContentDocumentLink cdl = New ContentDocumentLink();
        cdl.LinkedEntityId = 'a0a2F000002whylQAA';
        cdl.ContentDocumentId = testcontent.ContentDocumentId;
        cdl.shareType = 'V';
        insert cdl; 
        
        List<ContentDocument> cdoc = [SELECT Id, Title, LatestPublishedVersionId FROM ContentDocument where id=:testcontent.ContentDocumentId];
        
        delete cdoc;
    }

}