As I said above, the examiner will have to inform the candidate's competent authority of his intention to conduct the test/check/assessment and receive a briefing from them. This assumes, of course, that the candidate's competent authority has implemented the annexes to the Aircrew Regulation.
Note that there is no requirement for the examiner to obtain authorisation from the candidate's competent authority, he must merely inform them of his intention. The competent authority is then required by EU law to provide the necessary briefing.