I just got a "like new" battery from ebay and wanted to tested if that is true. Is there a battery tester program for this?

Compare your old and new batteries physically by looking at the sticker on them. If they both look the same, then you bought a genuine battery, which is a good thing. "Replacement" batteries should be avoided at all times.

If it’s a genuine battery, just go online and look up what the charge time should be for your laptop. If it lasts roughly that long with your screen brightness turned all the way down, then you did indeed buy a like-new battery.