Hi Jacob,
I'd assume you would want to verify the functions on the lightning connector assembly before you close it back up.
# Charging
# Computer connection
# Taptic Engine
# Microphones
# Speaker
# Cellular antenna
So connect everything back up, then plug in the battery. Power it up; that verifies display, touch screen and battery. Toggle the silent switch and verify the vibrator works. Use the voice recorder and play it back to check the microphones and speaker. Confirm you have a cell signal. Plug it into a computer and make sure it sees and can be seen. Finally plug it into a charger and make sure it charges.
That'll cover all of the services provided by the lightning port assembly. After going through that list, you can be reasonably confident your repair was successful.