Shut off while backing up, engine cranks but does not start?

Yesterday I went down the road to the store, put the car park, got out went in the store. When I got back in the car and cranked the car, it cranked just fine. I put it in reverse, and as I was backing out, it shut off on me. It was like it wasn’t getting gas and then I turned the car off tried to restart it and it just keeps on making the crank noise, but it never actually starts. My husband and them come and towed it and they thought that it might be the fuel pump. They took the fuel pump off and tested it and it’s saying that it’s good when they test it, so we don’t know what else it might could be they have checked the relays.