With the field in MotoGP being so incredibly tight, the value of testing has increased exponentially. The more equal the bikes and manufacturers are, the more important testing has become. Smaller and smaller gains are making a bigger and bigger difference.
But as part of Dorna and the FIM's attempt to control costs in MotoGP, testing has been reduced to the bare minimum. Beyond the bare minimum, perhaps; there will be two days of post-race testing in 2023, but next year, that number has been bumped back up to three days.
Post-race tests are a fantastic opportunity to try new things at a circuit where the teams have a whole weekend's worth of data. The downside is that the circuit is also covered in Michelin rubber, meaning the grip is spectacular, which can hide all sorts of problems. And in 2023, the two post-race tests are taking place at Jerez and Misano, useful circuits for sure, but not great places for trying new aerodynamics, as the top speed is limited, and there are few corners where you are accelerating from very low speeds.