Documentation is written using Racket's Scribble. The raw source is in manual.scrbl.
The HTML output that you'd actually want to read can be found on PLaneT.
You can also generate it using
./make-doc.sh, then point your browser to
rackunit tests use the submodule feature new in Racket 5.3. Tests are in
(module+ test ..). You can run the tests for a
foo.rkt file with
test foo.rkt. You can run tests for all files using
raco test ./.