unit tests and related matters

What's the best way to do unit tests?

Searching led to http://www.swi-prolog.org/pldoc/package/plunit.html, but it 
doesn't seem to come with my installation or be available as a Debian package.  
I'm using Debian wheezy amd64, which has SWI Prolog 5.10.4.

Eventually I  found http://www.swi-prolog.org/git/packages/plunit.git.

If that is appropriate to use, should I go with the current version, or the 
one tagged for V5.10.4?

I assume I then need to put that in an appropriate spot, probably compile it, 
and make sure prolog knows how to find it.  Any tips on that would be great, 
otherwise I can probably figure it out from the fine manual.

It would be nice if this kind of stuff were more obvious to  the uninitiate.  
Possibilities include
*on the front page "a rich set of contributed modules" with a link (yes I know 
the contrib link is on the left; that's how I eventually found them).
*A FAQ entry about how to locate, get and use contributed libraries, and 
possibly other stuff on git.
* Expand http://www.swi-prolog.org/git.html to include 3rd party libraries.
*  http://www.swi-prolog.org/pldoc/package/plunit.html describes how to get 
the library, or at least links to the software.

Thanks.
Ross Boylan