How to mock a file attachment size in Apex Salesforce to test

Question

I have to test a method that return a boolean false when the attachment upload is bigger than 25 megas, I tried to test this one using the code below but there is a limit dml exception string too long, besides I tried to cut them in pieces more smaller but the problem is with cpu apex clock, any idea to resolve this? Any help would be appreciated

    public static Boolean  verifySizeAttachment(String caseId){
    Boolean validation = true;
    AggregateResult[] lstAttachment = [SELECT  SUM(ContentDocument.ContentSize)
                                        FROM ContentDocumentLink
                                        WHERE LinkedEntityId =: caseId and 
                                        ContentDocument.Description = 'Send Email'];
        
    if(lstAttachment.size() > 0){           
        Double size = (Double) lstAttachment[0].get('expr0');          
        if(size > 25000000){                
            validation = false;                
            list<ContentDocumentLink> lstAttachmentDelete = [SELECT Id
                                                            FROM ContentDocumentLink
                                                            WHERE LinkedEntityId =: caseId and 
                                                            ContentDocument.Description = 'Send Email' limit 1];              
            delete lstAttachmentDelete;    
            }         
        }
        
        return validation; 
    }
    }

//TEST CLASSES

    //STEP 1
    ContentVersion version = new ContentVersion();
    version.Title= 'File Name';
    version.PathOnClient = 'sample.pdf';
    version.VersionData=blob.valueOf('Test Content data');
    version.Description= 'Send Email';
    insert version;
    
    version = [SELECT ContentDocumentId, ContentDocument.ContentSize FROM ContentVersion WHERE Id = : version.Id];
    
    //STEP 2
    ContentDocumentLink cdl = new ContentDocumentLink();
    cdl.ContentDocumentId = version.ContentDocumentId;
    cdl.LinkedEntityId = newCase.Id;
    insert cdl;
    
    
    Test.startTest();
    // VERIFY LESS THAN 25mb - TRUE
    Boolean validation =  AttachmentController.verifySizeAttachment(newCase.Id);
    System.assertEquals(true, validation);
    
    // VERIFY MORE THEN 25 MB - FALSE
   
    version.VersionData = Blob.valueOf(String.valueOf('a').repeat(26000000));
    update version;
    validation = AttachmentController.verifySizeAttachment(newCase.Id);   
    System.assertEquals(false, validation);

    Test.stopTest();
}

Answer 1

Change your code under test to:

public AttachmentController {
  @TestVisible Integer MAX_FILESIZE = 25000000;
  ...
  public static Boolean  verifySizeAttachment(String caseId){
  
    Boolean validation = true;
    AggregateResult[] lstAttachment = [SELECT  SUM(ContentDocument.ContentSize)
                                    FROM ContentDocumentLink
                                    WHERE LinkedEntityId =: caseId and 
                                    ContentDocument.Description = 'Send Email'];
    
    if(lstAttachment.size() > 0){           
    Double size = (Double) lstAttachment[0].get('expr0');          
    if(size > MAX_FILESIZE){                
        validation = false;                
    ... 
  }
}

Then dependency inject a smaller value to MAX_FILESIZE in the testmethod

//STEP 1 - create attachment bigger than max
AttachmentController.MAX_FILESIZE = 10;
ContentVersion version = new ContentVersion();
version.Title= 'File Name';
version.PathOnClient = 'sample.pdf';
version.VersionData=blob.valueOf('a'.repeat(MAX_FILESIZE); 
version.Description= 'Send Email';
insert version;

...
Boolean validation =  AttachmentController.verifySizeAttachment(newCase.Id);
System.assertEquals(true, validation,'attachment should be ok size');

//STEP 2 - create attachment bigger than max
Cversion = new ContentVersion();
version.Title= 'File Name';
version.PathOnClient = 'sample.pdf';
version.VersionData=blob.valueOf('a'.repeat(MAX_FILESIZE+1); 
version.Description= 'Send Email';
insert version;
...
Boolean validation =  AttachmentController.verifySizeAttachment(newCase.Id);
System.assertEquals(false, validation,'attachment too big');