An earlier test at 275 kilometres per hour took place in the presence of French Foreign Affairs Minister Jean-Yves Le Drian, who is in the country to monitor progress on the project, which is parly financed by a French loan.
"At 270-275 kilometres per hour, this is already the fastest train on the African continent," Le Drian commented during a ceremony to mark the signing of a loan to the ONCF by the French Development Agency.
France is providing 50 percent of the two-billion-euro cost, which is 15 percent higher than initial estimates published in 2007.
The rolling stock will be provided by France's Alstom engineering company.
The 350-kilometre link between Casablanca and Tangiers via the capital Rabat will cut journey times between the north African country's economic hubs by almost two-thirds, to just over two hours.
Difficult terrain and high winds on parts of the route have made some major engineering works, including the construction of 12km of viaducts, necessary.
A "Stop TGV" campaign was launched against the project, arguing that it was not a priority for the country and would not pay its way.