How to write a test class for Attachment, Messaging, Content Version Objects in Salesforce?

Hi Prachi,

To write a test class for Attachment, Messaging, Content Version Objects in salesforce you can take help from the following example:-

@isTest 
public class AttClassTest 
{
    static testMethod void testEx1() 
    {
        Account testAccount = new Account();
        testAccount.Name='Test Account' ;
        insert testAccount;
        
        Contact cont = new Contact ();
        cont.FirstName = 'FirstName';
        cont.LastName = 'LastName';
        cont.Email='email@email.com';
        cont.phone='12345678';
        insert cont;
        
        Account acct = new Account(Name='TEST_ACCT');
        insert acct;
        
        ContentVersion contentVersion = new ContentVersion(
            Title = 'Penguins',
            PathOnClient = 'Penguins.jpg',
            VersionData = Blob.valueOf('Test Content'),
            IsMajorVersion = true
        );
        insert contentVersion;    
        List<ContentDocument> documents = [SELECT Id, Title, LatestPublishedVersionId FROM ContentDocument];
        
        //create ContentDocumentLink  record 
        ContentDocumentLink cdl = New ContentDocumentLink();
        cdl.LinkedEntityId = acct.id;
        cdl.ContentDocumentId = documents[0].Id;
        cdl.shareType = 'V';
        insert cdl;
        
        System.Test.StartTest(); 
      <b>  PageReference pageRef = Page.aaaaaaaaaa; // Add your VF page Name here</b>
        pageRef.getParameters().put('Id', String.valueOf(acct.Id));
        System.Test.setCurrentPage(pageRef);
        AttClass cls = new AttClass();
        cls.Body =Blob.valueOf('Test Content') ; 
        cls.Name='Test' ;
        cls.save();
        AttClass.createContentVersion('Test',Blob.valueOf('Test Content'));
        AttClass.createContentLink(contentVersion.Id , acct.Id);
        cls.contentId =null ;
        cls.save();
        System.Test.StopTest();
    }
    
    
}

for more take help from https://developer.salesforce.com/forums/?id=9060G0000005ooMQAQ