The French team is well positioned to win another title after a strong start to this year's campaign, after pulling out a 145 point lead after just six races.
Drivers Leclerc and Alex Albon are separated by just a single point and are set to battle each other for the championship.
"I understood it straight away, as soon as I worked with them," Leclerc said. "They're a very serious team. By GP3 standards, what they do is really impressive."
"Sometimes, it really feels like being in an F1 team, with many fewer people obviously, but they're very serious. The debriefs are very serious. They're very experienced too, and all of this means they're dominant at the moment."
Bahrain International Circuit - Winter testing