While teams can be notoriously guarded as they ramp up preparations for the opening Grand Prix, four days of running - and hearing the thoughts of the drivers, team members and paddock in general - still offer tantalising glimpses into how the competitive order might play out.
So what were the revealing themes? Which teams looked most ominous - and which appear to be on the back foot already?
1. Ferrari have made massive progress…
The good news for fans wanting to see world champions Mercedes challenged is that the Scuderia appear to have taken huge strides forward.
The team made ‘very, very ambitious’ changes between their 2015 car and the new SF16-H, and the early signs suggest their bravery has been rewarded. “What I feel is that it is a very good step forward,” Sebastian Vettel enthused after his first day in the car - a view echoed by Kimi Raikkonen, who insisted his new prancing horse was an immediate improvement. Vettel also had the ‘honour’ of setting the fastest time of the four days, albeit on Pirelli’s new ultrasoft compound.
Exactly how big a step they have made, particularly relative to Mercedes, is the key question of course - and it is unlikely to be answered in full until qualifying in Australia.
As Raikkonen put it: “The car feels better than last year, the base line is strong, so we are where we want to be. It’s definitely a big step up. Will it be enough? We’ll see…”
2. …but Mercedes are ‘better than ever’
For two years running now, the Silver Arrows have faced the problem of how to improve on an already staggeringly dominant car. All the signs in Barcelona suggest they have produced another sensational machine.
From the very first morning, it was clear Mercedes had a plan in Spain: mileage. By the end of the first day Lewis Hamilton had completed 156 laps; by the end of the test, the team had racked up close to 700 laps, more than 10 race distances. The rest of the field couldn’t help but take notice.
It was, according to Fernando Alonso, proof that Mercedes were ‘better than ever’; or as Felipe Massa put it, a ‘big warning’ for Mercedes’ rivals.
Mercedes too were incredibly upbeat - Hamilton and Nico Rosberg both admitted they were staggered by the reliability of the F1 W07 Hybrid, while the latter said the massive mileage had also revealed - and allowed the team to fix - several small issues.
It wasn’t a total coup for the champions - they are yet to sample any of the new soft tyre compounds for example, meaning they are yet to fully gauge the outright potential of their new car. But the message was emphatically clear: Mercedes still look very much the team to beat in 2016.
3. McLaren have their work cut out
After a year of discontent, the 2015/16 off-season offered a chance of salvation for McLaren and their beleaguered Honda power unit - a chance to reset, learn lessons and return stronger. From the evidence of Barcelona, they are in a dramatically better position than 12 months ago - but they are still enduring niggling difficulties that need to be stamped out.
The first two days offered a lot of encouragement, as Jenson Button racked up 84 laps and then Fernando Alonso clocked up 119 - after which he also enthused that McLaren’s chassis was on the cusp of being the class of the field.
The final two days spoiled the momentum, however: Button was delayed on the third day, while Alonso managed a paltry three laps - none timed - on the fourth and final day. While their rivals were making hay, McLaren were consigned to the garage.
Honda’s new F1 chief Yusuke Hasegawa, admitted reliability problems have not yet been sorted. He also intimated that 4,000kms would be a healthy amount of mileage to achieve - the team ended the first test with a quarter of that total, on 1196.
The team now have two filming days at the circuit - an important chance to ensure the car is running properly again before four crucial days next week at the final pre-season test.
4. Haas have hit the ground running
The last time new teams entered F1 racing was back in 2010 - and on that occasion none of three new entrants drove at all in the first test - indeed one team didn’t complete a single lap over the course of the entire pre-season.
Haas are in a very different position: they elected to wait until 2016 to compete - 2015 had been mooted - so as to get their house in order. Even so, their first four days in F1 were beyond even their own expectations.
It wasn’t just the fact they racked up over 280 laps and 1300kms; or the fact the team gelled so quickly; or the way in which Romain Grosjean, a seasoned hand with new cars, was immediately convinced the car has the potential to score points. It was also how the team reacted to adversity.
On day one the front wing tucked underneath Grosjean on the main straight, highlighting a previously unknown issue with the construction. The response was immediate: Haas fashioned a new solution and ran at reduced speed for the rest of the day, and brought in a proper fix for day two. It was F1 efficiency at its finest, from a team who had not yet seen out their first 24 hours on the track.
5. The ultrasoft tyre will make a real difference
Barcelona also offered a first glimpse of Pirelli’s new ultrasoft tyre compound, introduced as part of the Italian tyre manufacturer’s commitment to spice up the show. While Barcelona isn’t ideally suited to the purple-marked tyre - which is aimed more at street circuits - it appears they have met their brief.
"It felt like another step on top of the supersoft and behaved like a softer compound, so that's good" was Daniel Ricciardo’s take on the new compound. “It was consistent and you can expect just a little bit more grip from it.”
Pirelli too were pleased, saying that while the high-degradation circuit did not suit their new tyre, initial feedback from teams was positive. They also hinted that the gains should be around 0.5-0.8s per lap - in other words exactly what Pirelli wanted.
WATCH: Analysis: Who impressed most in the first test?
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