Jenson Button says he's "pragmatic" about what McLaren may learn in Spain but is still hoping that it will be good news.
The Woking team has struggled this season, falling off the pace and falling out of contention.
Instead of racing for podiums and race victories, Button and his team-mate Sergio Perez are battling just to make it into the top ten although the last two results in China and Bahrain appeared to be a step forward.
The question of how much progress McLaren have made since the start of the season will be answered at next weekend's Spanish GP.
Run at the Barcelona circuit which played host to the final pre-season test, Spain will be a true indication of whether or not the struggling MP4-28 is moving forward - or backward.
"It's been difficult for the team to make consistent progress through the first four races, but I think returning to a circuit where we undertook two of the pre-season tests will give us a useful benchmark of our progress so far," Button explained.
"There's been a lot of talk about the importance of next weekend's upgrades; but, as with every upgrade, they're simply part of the series of continuous improvement that are made across the season.
"As always, there'll be elements of it that work, elements that perhaps work in a different way to what we'd anticipated, and elements that don't work, or perhaps require further work.
"That's life in modern Formula 1."
He added: "So I'm pragmatic about what we'll discover next weekend. Of course, I'm hopeful that it'll move us a step closer towards the destination."