Examiners Handbook:
When an attempt is taken as two flights both the enroute and general handling are to be completed by the same examiner.
Sections 1 and 4a,b and h are to be tested on both flights
Standards Doc 19
The PPL SKILL TEST is intended to be flown as a complete flight including navigation and general handling manoeuvres. However, as agreed between the applicant and the Examiner, the En Route Procedures Section 3 may be conducted as a separate flight.
So unless you have agreed to it, they can't do it!!!! Its your test and your call.