I keep an old headlight, and socket wired to clips, just for that purpose, especially when I charge batteries that are "old and assumed" un usable...
sometimes they jump back to life tho, after fully charging and draining a while, then charged again... I always "load" a new battery once charged, especially when I use my tender on one for a spell... I clip the light to the batt, let it glow for 30 seconds, and check Volts, then remove the light, and recheck volts, and let it sit for 10 minutes, and recheck again,
this gives some idea of charged volts, loaded, and if the cell comes back to life on it's own by chemical reaction.
It isn't a viable load test by any means tho... just tells me if the battery is chargeable, and if i should continue or toss it.