Are you talking about PPL or CPL Skill Test? 'Radio Navigation' is NOT a required part of the PPL Skill Test - you merely have to be able to fix your position by use of aircraft radio navigation aids except GPS or ground-based radar and to track to or from a beacon for 5 minutes. You may use pre-planned radio navigation or GPS fixes to confirm visual fix points, but only at the Examiner's discretion.
The Examiner has certain guidelines as to pass/fail standards; don't worry too much about them and just do your best. Your instructors won't have put you up for the test unless they thought that you were ready for it!