Photos from the test showed Charles Leclerc's brother Arthur driving the 2023 Ferrari SF-75 with fully covered front and rear full-wet tyres. The guards include two holes in front but are fully covered at the back.
The Italian squad's reserve driver Oliver Bearman ran behind Leclerc in a 2024 car to check the visibility.
Formula 1's ruling body, the FIA, had run the first version of the spray guards during testing at a wet Silverstone last year as it attempted to find a solution that would improve visibility for the following cars in rainy conditions.
Although no actual images of the test were shared, the FIA did offer some 3D renders of the solution, which consisted of partial wheel covers on both the front and the rear tyres.
The test was carried out by Mercedes' reserve driver Mick Schumacher, with McLaren's Oscar Piastri used as a control running behind.
The conclusion from the first test was that the system made no significant difference to the levels of spray produced by the cars.
"What was done at Silverstone, with the help of Mercedes who created parts and McLaren [who ran a car to get feedback on spray] was perhaps too optimistic an experiment," the FIA's single-seater director Nikolas Tombazis told Autosport last year.
"The spray guards covered too little of the wheel. I was quite sceptical and imagined that we wouldn't see important results."
As a result, the FIA promised a more aggressive solution, which Ferrari took to the track on Thursday at Fiorano.
Tombazis explained last year how complex it was to find a solution that would work successfully.
"Having started this project towards the end of last year, and done quite a lot of CFD simulations, we did understand quite soon that it was not quite as simple as just put something on, off you go, and you're done," he said.
"We didn't want to lose too much performance of the cars and mess up the aerodynamics too much, although some of it is inevitable.
"And the actual aerodynamic load on these big mudguards or whatever you call them, if you have a complete cover, that would have quite high dynamic load. And therefore their support on the uprights would have to be fairly robust to not fly off at 300km/h."
On Friday, Ferrari will use a filming day to shake down the new aero package for next week's Emilia Romagna Grand Prix.
