In recent years, pre-season testing has slimmed down from two four-day tests, then predominantly in Barcelona, to just a single three-day test in Bahrain.
But while holding a shorter test at the same venue as the season opener is more efficient and cost-effective for teams, Alonso feels drivers are being shortchanged by a lack of practice.
Teams are just using one single car each day, which thanks to modern simulation tools is usually enough to prepare for the new season.
But it also means drivers get just one day and a half to adjust to the new machinery, having to hope there are no early glitches or gremlins that eat into the reduced run plan.
"We have a very limited testing in Bahrain," Alonso said. "I've been thinking all winter about this, how unfair it is that we only have one day and a half to prepare a world championship.
"There is no other sport in the world, with all the money involved and with all the marketing and the good things that we say about Formula 1 and being closer and closer to the fans, [where that happens].
"I cannot understand why we then go to Bahrain for four days, which could be two and two for the drivers. If you go to three, which is not even, which is an odd number, you cannot divide between the drivers.
"And I don't know why we don't go with two cars. Because we are already in Bahrain and we race the following week."
Alonso is not the only driver who has led calls to open up winter testing to two cars, with Mercedes man and GPDA director George Russell also behind the idea.
"Personally speaking, I don't think three days is enough, because you have got to remember from a driver's perspective, that is one and a half days per driver," Russell said last year.
"Could you imagine Rafael Nadal spending 12 weeks without hitting a ball and then going straight into the French Open with one and a half days of training? It just wouldn't ever happen.
"I understand and recognise why we do that. I think three days with two cars would probably be a good place to be."
