Before Australia every single F1 pundit, from Gary Andersson to guys at SkyF1 was talking how Ferrari looks mighty, how Ferrari is planted and that this could finally be their year. And when Australia came they were all saying that Melbourne is a specific track and that their bad performance is probably a fluke. Then came Bahrain, Ferrari was good there, and they were all like "we told you so". So no, those in the know didn't suspect that Ferrari's pace in testing wasn't real.
First of all: there were only 2 days of testing so far. Mercedes was nowhere near their yesterday's speed. Did they somehow forgot how to go fast over the night?
Second: Prove it.
Well, they are at the bottom of the speed traps with, at least "those in the know" are saying that for 2 years now, what is the most powerful PU. And they weren't even using DRS yesterday.