Add tests for rot13.el

* lisp/rot13.el (rot13): Docstring correction.

* test/lisp/rot13-tests.el: New file with tests for rot13.el.

1 files changed, 4 insertions, 1 deletions

diff --git a/lisp/rot13.el b/lisp/rot13.el
index ee4f51d7ff3..55725473eaa 100644
--- a/lisp/rot13.el
+++ b/lisp/rot13.el
@@ -63,7 +63,10 @@
 
 ;;;###autoload
 (defun rot13 (object &optional start end)
-  "Return ROT13 encryption of OBJECT, a buffer or string."
+  "ROT13 encrypt OBJECT, a buffer or string.
+If OBJECT is a buffer, encrypt the region between START and END.
+If OBJECT is a string, encrypt it in its entirety, ignoring START
+and END, and return the encrypted string."
   (if (bufferp object)
       (with-current-buffer object
         (rot13-region start end))