I use this little script a lot: to test my posts to
c.l.py, to test my articles, and to test my libraries.
Since the script is extremely simple and useful, I thought I
will share it.

The first thing you need is a text like this, with
cut and pasted interpreter sessions:

>>> 1 + 1
2

The doctester will look for snippets of this form and will
test them. The magic is performed by the doctest module in the
standard library. I have just added the possibity of inserting
named modules in the text file, like this one::

 #<example_module.py>

 a = 1

 #</example_module.py>

The doctester will extract code like this and save it in your
current directory, under the name ``example_module.py``,
*before* running the tests. In this way you can import
the module in your tests:

>>> from example_module import a
>>> print a
1

You may define any number of modules in the same way. 
You can also add code to a previously defined module, simply by
repeating the module name::

 #<example_module.py>

 b = 2

 #</example_module.py>

>>> from example_module import b
>>> print b
2

Ideally, in future extensions, it will be possible to insert snippets
of code in other languages (for instance bash).

The doctester can be used from the command line or called from
an external program. For instance, you could pass to the doctester
this text you are reading now: suppose it is stored in a file
called doctester.txt, you will get

::

 $ python doctester.py < doctester.txt
 doctest: 0 failed of 5

or, if you prefer a more explicit output,

::

 $ python doctester.py -v < doctester.txt
 Trying:
     1 + 1
 Expecting:
     2
 ok
 Trying:
     from example_module import a
 Expecting nothing
 ok
 Trying:
     print a
 Expecting:
     1
 ok
 Trying:
     from example_module import b
 Expecting nothing
 ok
 Trying:
     print b
 Expecting:
     2
 ok
 1 items passed all tests:
    5 tests in <current-buffer>
 5 tests in 1 items.
 5 passed and 0 failed.
 Test passed.

The message says that the tests were defined in '<current-buffer>': the
reason is that I usually call the doctester from Emacs, when I am editing
the text. If you have Python 2.4 and the doctester in installed in
your current Python path, you can just put the following in your .emacs::

 ;; passing the current buffer to an external tool
 (defun run-doctest ()
   (interactive)
   (shell-command-on-region (beginning-of-buffer)
                            (end-of-buffer)
                            "python2.4 -m doctester"
                            current-prefix-arg
                            current-prefix-arg))

 (defun run-doctest-verbose ()
   (interactive)
   (shell-command-on-region (beginning-of-buffer)
                            (end-of-buffer)
                            "python2.4 -m doctester -v"
                            current-prefix-arg
                            current-prefix-arg))

 ;; F6 for regular output, SHIFT-F6 for verbose output
 (global-set-key [f6] 'run-doctest)
 (global-set-key [(shift f6)] 'run-doctest-verbose)


If you have Python 2.3 you may have to work a bit more, or 
may just insert the full pathname of the doctester script. 
Obviously you may change the keybindings to whatever you like.
I am pretty sure you can invoke the doctester from the Other Editor 
(TM) too ;)