Test Class for Page Reference

opportunity opp= new opportunity();
opp.name='pradeep';
opp.accountid= acc1.id;
opp.closedate= date.parse('12/12/12');
opp.StageName='credit approved';
opp.Funding_Type__c='$';

insert opp;

ApexPages.StandardController sc = new ApexPages.standardController(opp);
OppExtension e = new OppExtension (sc);