Bench testing the old pump won’t prove anything. When a car with a fuel pump failure comes in we sometimes pound on the bottom of the fuel tank to rattle the pump. If the engine starts we can dive the vehicle into the shop for repair. By the time the pump is handed to you it will have been jarred and working.
There is an old service bulletin that indicates a problem with the fuel pump module, the plastic housing and internal lines. I suspect your mechanic only replaced the motor, not the complete assembly.
If your fuel pump has failed you could replace it yourself, it is so easy you can do it in a parking lot. The guy in this video is replacing the complete fuel pump module. He is improvising with the removal of the lock ring with a hammer and board, we have a spanner wrench for that.
How to replace the fuel pump on a 2005 Toyota Corolla - Bing video