Red Bull Racing and Ferrari have changed their testing plans for next month and will now run at Barcelona from March 2-5.
The test was originally scheduled from March 1 to March 4 - Thursday to Sunday - but Ferrari opted to test from Friday to Monday instead.
Red Bull consulted with Ferrari if they could join the Italian squad on track on Monday, with the Maranello squad giving its rivals the green light.
Both teams will still test just four days like their rivals, but will kick off their programmes a day later.
Red Bull team boss Christian Horner said the decision was made purely for logistical reasons.
"We have decided to join Ferrari in running from Friday to Monday as opposed to Thursday to Sunday. We're just moving it a day," Horner told AUTOSPORT.
"From a logistical perspective, it just made a bit more sense. We asked Ferrari if we could join them, they agreed.
"It's in the test agreement and also within the test regs. We are within the time limit for that. It's something that we've elected to do. Lotus are doing their own thing but that's for different reasons elsewhere."
Lotus is set to be granted a private day of testing after pulling out of the Barcelona test this week because of problems with its chassis.