Self-testing.

So there is new feature in the renderer available.

It is a testing framework from the "Practical Common Lisp" book. The book is awesome and I recommend it for reading for everyone who did not read it yet.

Anyway, I took the "framework" as it is without changes: it suits well as it is.

So, not too much, but the code is revisited a little bit and, anyway, it is a progress.

One small step is better than nothing...

By the way, on the picture one can see the new "checker" shader: it shows V direction with white and U direction with solid color, putting the round mark at the first vertex in the list.