To prevent your sump pump from malfunctioning, you can ensure that the sump pit is clean and clear of debris, keep the discharge line clear and check the sump pump's voltage.
You can test your sump pump by pouring a bucket of water into the sump basin and observing if the float switch activates and the pump turns on. You can also check for proper discharge of water by observing where the pump is discharging the water.
A battery backup for a sump pump is not necessary, but it can be a good idea to have one in case of a power outage. This will ensure that the sump pump can still operate and prevent flooding in the event of a power failure.