How to create apex tests unit for create pdf from visualforce page and save as attachment in Salesforce | Apex unit test for pdf attachment in Salesforce | Unit test for apexpages.standardcontroller test class | Test class for pagereference method in salesforce

  public class saveVfPdfCtrl {

    public String MstrId{GET;SET;}

    public Account accObj{GET;SET;}    

    public String PDFNo{GET;SET;}    

    public String baseURL{GET;SET;}

    public PageReference Cancel()

    {

        PageReference Pdf = NEW PageReference('/'+MstrID);

        pdf.setredirect(TRUE);

        RETURN Pdf;

    }

    public saveVfPdfCtrl(ApexPages.StandardController Controller){

        baseURL = URL.getSalesforceBaseUrl().toExternalForm();

        MstrId = ApexPages.currentPage().getParameters().get('id');

        accObj = [SELECT Id, Name, Phone, Industry, Rating, Description, Website, TYPE, (SELECT Id, Name, FirstName, LastName, Email, AccountId, Phone, Title FROM Contacts) FROM Account WHERE Id =: MstrId ];

    }

    public PageReference pdfAction()

    {

        PageReference savepage ;

        savepage = Page.savePdfVp;

        savepage.getParameters().put('id',MstrID);

        system.debug('id:- '+MstrID);

        BLOB pdfBlob;

        IF (!Test.isRunningTest()) {

            pdfBlob = savepage.getContent(); //generate the pdf BLOB

        } ELSE { 

            pdfBlob = BLOB.valueOf('Test');

        }

        List<ContentDocumentLink> notesattch = [SELECT id, ContentDocument.Title,LinkedEntityId FROM ContentDocumentLink WHERE LinkedEntityId =: MstrID ORDER BY ContentDocument.Title ASC];    

        system.debug('notesattch## ' + notesattch);

        IF(notesattch.size() > 0)

        {

            string title =  notesattch[0].ContentDocument.Title;

            system.debug('title111 ' + title);

            List<String> titleSplit = title.split('R');

            //String FinalTitle = titleSplit[0]+'R0'+notesattch.size();

            String FinalTitle = 'PO'+notesattch.size();

            system.debug('FinalTitle22 ' + FinalTitle);

            PDFNo=FinalTitle;

            ContentVersion conVer = NEW ContentVersion();

            conVer.ContentLocation = 'S'; // TO USE S specify this document IS IN Salesforce, TO USE E FOR external files

            conVer.PathOnClient = FinalTitle+'.pdf'; 

            conVer.Title = FinalTitle; 

            conVer.VersionData = pdfBlob;

            system.debug('conVer@@ ' + conVer);

            INSERT conVer;  

            Id conDoc = [SELECT ContentDocumentId FROM ContentVersion WHERE Id =:conVer.Id].ContentDocumentId;

            ContentDocumentLink conDocLink = NEW ContentDocumentLink();

            conDocLink.LinkedEntityId = MstrID;

            conDocLink.ContentDocumentId = conDoc; 

            conDocLink.shareType = 'V';

            INSERT conDocLink;

            UPDATE accObj;

             PageReference pageRef = NEW PageReference( baseURL+'/lightning/r/Account/' + System.currentPageReference().getParameters().get('id')+'/view');

            pageRef.setRedirect(TRUE);

            //system.debug('pageRef@@@ ' + pageRef);

            RETURN pageRef;

        }

         ELSE{RETURN NULL;}

    }

}

  @isTest

public class saveVfPdfCtrlTest {

    static testmethod void validateStandardController(){

            Account acc = NEW Account();

            acc.Name='test'; 

            INSERT acc;

            Contact  con = NEW Contact();

            con.FirstName='test';

            con.LastName='test';

            con.AccountId=acc.Id;

            INSERT con;

           ContentVersion content=NEW ContentVersion(); 

            content.Title='Header_Picture1'; 

            content.PathOnClient='/' + content.Title + '.pdf'; 

            BLOB bodyBlob=BLOB.valueOf('Unit Test ContentVersion Body'); 

            content.VersionData=bodyBlob; 

            content.origin = 'H';

            INSERT content;

            ContentDocumentLink contentlink=NEW ContentDocumentLink();

            contentlink.LinkedEntityId=acc.id;

            contentlink.contentdocumentid=[SELECT contentdocumentid FROM contentversion WHERE id =: content.id].contentdocumentid;

            contentlink.ShareType = 'I';

            contentlink.Visibility = 'AllUsers';         

            INSERT contentlink;

           ContentVersion cvlist = NEW Contentversion(); 

            cvlist.Title = 'CZDSTOU'; 

            cvlist.PathOnClient = 'test'; 

            cvlist.VersionData = EncodingUtil.base64Decode('Unit Test Attachment Body'); 

            List<ContentVersion> cvl = NEW List<ContentVersion>(); 

            cvl.add(cvlist); 

            INSERT cvl;

          Test.startTest(); 

           ApexPages.Currentpage().getParameters().put('id',acc.Id);

           ApexPages.StandardController sc = NEW ApexPages.StandardController(acc);

           saveVfPdfCtrl controller1 = NEW saveVfPdfCtrl(sc);

           controller1.pdfAction();

           controller1.Cancel();

        Test.stopTest();

    }

}