I'm sure it was Ron Dennis who said he has no interest in winning the winter world championship
Testing obviously has the potential to tell you very little. Teams have been known to run laps with different sectors being fast and others not so, they then piece together the good bits without fully revealing their hand.
I read that McLaren were so close to the limit last year that several times in races the pit wall were really expecting the cars not to manage to get to the end. I presume they don't just mean engines, but other systems on the car too.
As for Alonso, it seems like a great career move - who's to say how long Renault will be in F1 and you can never write Mclaren off, even in a bad year they are better than most.