A week ago my car overheated so i let it cool off then filled the coolant. i drove it around to see if it'd overheat again and it slowly did. when i stopped i heard popping til i turned off the car and there was a river of coolant flowing away from my vehicle. My car has been at the shop for a week now and he said he ran a pressure test and there was no leak. whats wrong with my car?

he says he ran the car for awhile and it hasnt overheated, but he hasnt drove it yet