The squad has allocated one of its straightline/constant radius days for this test, with the results dictating which parts are used in Friday practice at Silverstone.
It is hoped that the parts, which early indications suggest have performed well, will allow McLaren to claw back some of the downforce deficit to the frontrunners as well as boosting its understanding of the car.
Briton Oliver Turvey was in charge of driving duties.
"The only issue with our car is we lack downforce and that is what we are trying to create at the moment," said McLaren managing director Jonathan Neale.
"We are in Idiada at the moment. I spoke to the guys at lunchtime today, the weather has been kind to us and it looked set for a productive afternoon.
"But we are not there just for testing parts, we are there testing some fundamental understanding issues as well.
"We will wait until Friday afternoon at Silverstone to see what remains on the car for Saturday as to how successful it has been.
"We won't know until this evening finally what package we are going to take [to the British GP]."
Although McLaren has not been able to close the gap to the leading teams as quickly as hoped, Neale insists it remains committed to working on its current car.
This programme is expected to have some impact on the design of the 2014 car, meaning that McLaren is determined to continue to increase its understanding of the troublesome MP4-28.
"In terms of this year's car versus next year's car, we are still learning a lot," said Neale.
"There are some programmes on the car that we will want to run through until much later into the season which is important for next year as well.
"There isn't going to be a golden bullet. We are pushing hard but the reality of the situation is there is still a big gap from us to the front of the grid."
After failing to score a point in the previous race in Montreal, Neale is hopeful of McLaren running in the top 10 at Silverstone this weekend.
He has targeted getting both cars into the top 10 qualifying shootout and contending for points but accepts a podium finish is a long-shot.
"We want to get both cars into Q3 and then race hard for good points," he said.
"It would be great if the guys could get a podium out of it but I think on recent performance that could be quite challenging.
"But F1 is a fickle sport and you never know what is going to happen until the last lap."
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