setCreatedDate() can be used to set CreatedDate for records in Test Class in Salesforce.
Sample Code:
Account a = new Account(name=’myAccount’);
insert a;
Test.setCreatedDate(a.Id, DateTime.newInstance(2012,12,12));
Note:
1. Don’t use seeAllData=true.
2. Make sure setCreateDate method is called before Test.start method.
Cheers!!!