They have validated the concept with mockups and breadboards (It’s why you see the cables running out of the back of those vehicles) but this does represent a step forward for the howitzer variant of the Future Combat System:

The mobile cannon, which is crewed by two soldiers, has a fully automated ammunition loading system and on-board projectile tracking. Lieutenant Colonel Robert McVay, Army Product Manager for NLOS-C said in a statement that “This marks the first 155mm round fired from a fully automated howitzer mounted on an FCS hybrid-electric chassis and remotely commanded through its on-board computers and controls.”

You will note in the picture that this is not the full up model firing, but one of the breadboard models, note the cables out the rear.