Honda released images of tester Oliver Turvey driving the interim MP4-29H car.
Nov.15 (GMM) McLaren's new works Honda era got up and revving at Silverstone on Friday.
The test, allowed under F1 regulations because it was for 'filming' and with promotional Pirelli tyres, took place behind closed doors.
But on Twitter, Honda released images of tester Oliver Turvey driving the interim MP4-29H car - bearing the word 'Honda' on its engine cover - out of the pits.
It is likely to be tested in earnest at the post-race Abu Dhabi test.
"First ever shot of the McLaren Honda. Start of a new era!" said the Japanese manufacturer on Twitter.
Meanwhile, McLaren denied rumours the Red Bull-backed Spanish youngster Carlos Sainz jr is a dark horse candidate to join his countryman Fernando Alonso at the team in 2015.
The Spanish sports daily AS, however, insists there is some truth to the rumour, adding that Sainz would be backed by the potential sponsor Movistar and could be signed as a test driver.
But AS acknowledged that the Sainz camp also denied the reports.