Regarding a job position which:

• Does not seek to replace someone else;
• It's not about a new employee;
• The person is entitled to work as the Chief/Head of the Department with the command of the CEO, to see how this person will handle this position for a certain period of time until entitled permanently or not at all.

I don't want to use the term "temporary", nor "interim", which is used in times of turmoil.

Can you suggest a more appropriate term given the situation above?