Sergey Sirotkin has vowed to keep the respective secrets of the Renault and McLaren teams to himself.
The Russian, already Renault's reserve driver, has now been signed by Renault-powered McLaren in the same role.
"The work is similar in both teams," Sirotkin told Russia's Championat at Paul Ricard.
"We have yet to discuss how I will divide my time, but on Friday I signed a paper to strictly not disclose information about the simulator, the work on the track, or any other things about the two teams."
Sirotkin also indicated that his Renault role will take precedence, for example in the event that both teams need a reserve driver at the same race.
"That's a difficult question, but I think the priority will be Renault. That is my assumption," he said.
