McLaren's new engine partnership with Honda got off to a difficult start at the post-season Abu Dhabi test.
The car suffered recurring electrical problems which limited it to just five laps over the two days of the test, none of them at racing speed.
McLaren racing director Eric Boullier admitted the test was "difficult" but insisted conducting it was "positive".
He said McLaren were testing to try to identify problems that would otherwise have affected them in pre-season.
"This is just part of the learning experience we expected when we took on the interim car programme," said Boullier.
"It's useful to discover these issues pre-Christmas, as it allows us to deepen our understanding of the integration between power-unit, ancillaries and the car.
"I'd rather be ironing out these problems in Abu Dhabi than discovering them in Jerez next February.
"It's definitely been a positive for both McLaren and Honda to conduct this test - there have been some troublesome issues, but we've made progress."
McLaren, for whom reserve driver Stoffel Vandoorne was conducting testing in Abu Dhabi, have yet to confirm their driver line-up for 2015.
Double world champion Fernando Alonso is to join the team from Ferrari, although McLaren have not officially admitted his move.
Chairman Ron Dennis has not yet decided which of his 2014 drivers, Jenson Button and Kevin Magnussen, to retain alongside the Spaniard.