This is one of the latest EASA proposals for amending the Aircrew Regulation:
Examiners shall not conduct:
(a) skill tests or assessments of competence of applicants for the issue of a licence, rating or certificate:
(1) to whom they have provided more than 25% of the required flight instruction for the licence, rating or certificate for which the skill test or assessment of competence is being taken
However, this depends on a forthcoming EC vote and it is
NOT guaranteed that it will definitely be adopted.