"Testing" a computer is so very simple, basically all it takes is a monitor, keyboard, and mouse(in a very minimal space). Plug it up, turn it on, that's it! Of course there are lots of more extensive ways to "test" one, but if it turns on, boots up, and is receptive to applications etc, there's probably not a whole lot wrong with it. Learn how to find the recovery partition if it has one, and do a complete recovery, that will remove everything it had, including personal information and even viruses, basically restoring it to "from factory".