You start an engine at the gate with APU bleed air is unavailable. A ground air, or huffer, cart is used to provide the air pressure to start the engine. After pushback, and usually away from the gate area, the second engine is started using bleed air from the first.

Minor damage on fan blades is blended to smooth it out and remove any sharp angles that would lead to cracks. The same thing is done on metal propellers on prop planes. The engine run would have been to check for any excessive vibrations, not to see if the repair would hold. Such repairs are very common.