Ex-Formula 1 driver Scott Speed will drive Andretti Autosport's Formula E car in this week's Donington Park test, with series ambassador Gil de Ferran also trying the Spark-Renault.
Michael Andretti's team has so far only announced Franck Montagny as a driver for its FE squad.
Speed, who raced in F1 with Toro Rosso from 2006 to mid-'07, now drives for Andretti's factory Volkswagen programme in the US-based Global RallyCross Championship.
"I'm excited to get into a single-seater again," said Speed.
"I expect it to be a very steep learning curve seeing as I haven't driven anything with downforce in seven years.
"The Andretti organisation has been an amazing company to drive for, and I'm happy to grow my role as one of its drivers while helping out with the Formula E test."
Andretti intimated that Speed was not necessarily a contender for an FE race seat.
"Scott is one of our contracted drivers with great open-wheel experience, so we're happy to have him fill the seat while we evaluate options for our second full-time Formula E drive," he said.
Two-time CART champion and 2003 Indianapolis 500 winner de Ferran recently signed up as an ambassador for FE, and is sampling the Andretti car as part of his role.
"I have been very curious and interested in how an electric-powered racing car would behave and handle," said de Ferran, who has not raced regularly since driving for his own team in the American Le Mans Series in 2008-09.
"Obviously I haven't driven anything feverishly for over five years, so it will be certainly a challenge but something that I am really looking forward to."
The Formula E test at Donington takes place on Thursday and Friday this week.