Why is my patch failing a test? When a patch fails testing because it doesn't apply, and the error reads "Ensure the patch applies to the tip of the chosen code-base." what does this mean?
Basically your patch have to be applyable with the command

patch -p1 &lt; $filename.patch


http://drupal.org/node/707484 is a pretty good tutorial how to create patches so the testbot can use it.