Hi, novice here.

I have a Contact module on which I upload files(generally images) from the default File upoading function(PFA). I have used an after insert trigger to generate public url and made it visible. Then this URL is saved in a custom field of Contact module. It works fine. But when I write test class for this process, it doesn't work. Upon investigationl l found that the SObject it gives is 'User' for some reason, even though I linked it to a contact. I am sharing the original trigger code as well as test class for it. What am I doing wrong? Please guide.

Trigger 1-

trigger ContactFileLinkTrigger on ContentDocumentLink (before insert) {

    if(Trigger.isBefore){
        
        for(ContentDocumentLink l:Trigger.new) {
            l.Visibility='AllUsers';
        }
    }    
}

Trigger 2-

trigger ContactFileVersionTrigger on ContentVersion (after insert)
 {

    checkFileParent(trigger.New);
    
    public static void checkFileParent(List<ContentVersion> contentVersions){
       
        set<Id> contentDocumentIdSet = new set<Id>();
        map<Id, ContentVersion> contentDocumentIdVersionListMap = new map<Id, ContentVersion>();

        for(ContentVersion objContentVersion : contentVersions){
                    contentDocumentIdSet.add(objContentVersion.ContentDocumentId);
            contentDocumentIdVersionListMap.put(objContentVersion.ContentDocumentId, objContentVersion);
        }
		
        if(!contentDocumentIdSet.isEmpty())
        {
            List<ContentDocumentLink> contentDocumentList = [select LinkedEntityId, ContentDocumentId from ContentDocumentLink WHERE ContentDocumentId in :contentDocumentIdSet];

            system.debug('contentDocumentList: ' + contentDocumentList);
            
            if(contentDocumentList.size() > 0)
            {
                List<ContentVersion> validContentVersionList = new List<ContentVersion>();
                Map<Id, contact> versionIdContactIdMap = new Map<Id, contact>();
                for(ContentDocumentLink ContentDocumentSingle:contentDocumentList)
                {    
                    system.debug('ContentDocumentSingle: ' + ContentDocumentSingle.LinkedEntityId.getSObjectType().getDescribe().getName());
                    String documentSOject = ContentDocumentSingle.LinkedEntityId.getSObjectType().getDescribe().getName();
                    //if(documentSOject == 'Contact' || (Test.isRunningTest() && documentSOject == 'User') )
                    if(documentSOject == 'Contact')

                    {
                    	validContentVersionList.add(contentDocumentIdVersionListMap.get(ContentDocumentSingle.ContentDocumentId)); 
                        versionIdContactIdMap.put(contentDocumentIdVersionListMap.get(ContentDocumentSingle.ContentDocumentId).Id, [Select Contact_Image_URL__c, Contact_Image_Name__c FROM Contact WHERE id=:ContentDocumentSingle.LinkedEntityId LIMIT 1]);
                    }
                }
                
                if(validContentVersionList.size() > 0)
                {
                    createPublicLinkForFile(validContentVersionList, versionIdContactIdMap);
                }
            }
        }
    }
    
    public static void createPublicLinkForFile(List<ContentVersion> contentVersions, Map<Id, contact> versionIdContactIdMap)
    {
        ContentDistribution[] distributionsToInsert = new List<ContentDistribution>();
        set<Id> contentDistributionSet = new set<Id>();
        map<Id, ContentVersion> contentDistributionIdContentVersionMap = new map<Id, ContentVersion>();
       	for(ContentVersion objContentVersion : contentVersions){
            //if image uploaded then only create public link
            //if(objContentVersion.ContentDocumentId.ParentId.getSobjectType()==Contact.SobjectType){
                ContentDistribution getDist = createContentDistribution(objContentVersion.Id);
                //distributionsToInsert.add(createContentDistribution(objContentVersion.Id));
                distributionsToInsert.add(getDist);
            	system.debug('objContentVersion');
            	system.debug(objContentVersion);
            	contentDistributionIdContentVersionMap.put(objContentVersion.Id, objContentVersion);
                if(!contentDistributionSet.isEmpty())
                {
                    contentDistributionSet.clear(); 
                }
            	contentDistributionSet.add(objContentVersion.Id);
            //}
        }
        system.debug('distributionsToInsert: ' + distributionsToInsert);
        if(!distributionsToInsert.isEmpty())
        {
        	insert distributionsToInsert;
            List<ContentDistribution> contetDistributionList = [select ContentDownloadUrl, ContentVersionId from ContentDistribution WHERE ContentVersionId in :contentDistributionSet];
			
            system.debug('ContentDistribution: ' + contetDistributionList);
            system.debug('ContentDistribution url: ' + contetDistributionList[0].ContentDownloadUrl);
            
            List<contact> contactToUpdateList = new List<contact>();
            for(ContentDistribution contetDistributionsingle:contetDistributionList)
            {
                
                contact contactToUpdate = versionIdContactIdMap.get(contetDistributionsingle.ContentVersionId);
                
                contactToUpdate.Contact_Image_URL__c = contetDistributionsingle.ContentDownloadUrl;
                contactToUpdate.Contact_Image_Name__c = contentDistributionIdContentVersionMap.get(contetDistributionsingle.ContentVersionId).Title + '.' + contentDistributionIdContentVersionMap.get(contetDistributionsingle.ContentVersionId).FileType;
                
                contactToUpdateList.add(contactToUpdate);
            }
            
            if(contactToUpdateList.size() > 0)
            {
            	update contactToUpdateList;   
            }
        }
    }
    
    public static ContentDistribution createContentDistribution(Id contentVersionId){
        ContentDistribution newDist = new ContentDistribution();
        newDist.ContentVersionId = contentVersionId;
        newDist.Name = 'External Link';
        newDist.PreferencesNotifyOnVisit = false;
        newDist.PreferencesAllowViewInBrowser = true;
        newDist.PreferencesAllowOriginalDownload=true;
        system.debug('createContentDistribution created');
        system.debug(newDist);
        return newDist;
    }
}

I also tried to modify the code with SObject Type as User but then the test class just generates an error. (PFA)

Test Class (Excerpt code)-

@isTest
private class ContentDocumentLinkVisibilityHandlerTest {
    @isTest static void ContentDocumentLinkTriggerTest() {
        Test.startTest();
 
        Account accountObj = new Account();
        accountObj.Name = 'CRECAccount';
        INSERT accountObj;
        
        Contact contactObj = new Contact();
        contactObj.FirstName = 'CREC';
        contactObj.LastName = 'Project';
        contactObj.Email = 'abc@CERC.com';
        contactObj.AccountId = accountObj.Id;
        INSERT contactObj;
        
        ContentVersion content1 = new ContentVersion(); 
        content1.Title = 'Header_Picture1'; 
        content1.PathOnClient = '/' + content1.Title + '.jpg'; 
        Blob bodyBlob1 = Blob.valueOf('snc'); 
        content1.VersionData = bodyBlob1; 
        content1.origin = 'H';
        insert content1;
        ContentDocumentLink contentlink1 = new ContentDocumentLink();
        contentlink1.LinkedEntityId = contactObj.id; // linked with contact module
        contentlink1.contentdocumentid = [select contentdocumentid from contentversion where id =: content1.id].contentdocumentid;
        // contentlink1.ShareType = 'I';
        contentlink1.Visibility = 'AllUsers';
        insert contentlink1;
        Update contentlink1;
  
        Test.stopTest();
    }
}