Stalls at idle

I was driving my car last week and it died. I got a jump but the car died after a couple of minutes. I than put my sister's battery in my car to drive it home. It worked fine. So I thought it was the battery. I tookj the battery to autozone they said the battery is fine. I thought maybe they were wrong and bought a new battery ( it work with my sister's battery so maybe it would work with a new one). It started fine but died again and only will stay on when I have my foot on the gas. I than took the alternater in and they said that was fine. So I checked the spark plugs and wires and the battery wires. I dont know what could be wrong.