lstObject=[select id, name from Object__c];

for(Object__c obj: lstObject){

          //Create Pagereference
         PageReference pg=new Pagereference('/apex/GeneratePDF?id='+obj.id);
        /* Above GeneratePDF page create PDF for one records successfully */

         if(!Test.isRunningTest()){
             b=pg.getContent();
         }
         else{
             b=Blob.valueOf('No Payslip were found for'+objPayslip.Employee__c);
         }
    }