Fixed a link in topics/testing/overview.txt

    $ ./manage.py test

Test discovery is based on the unittest module's `built-in test discovery`.  By

default, this will discover tests in any file named "test*.py" under the

current working directory.

.. _built-in test discovery: http://docs.python.org/2/library/unittest.html#test-discovery

Test discovery is based on the unittest module's :py:ref:`built-in test

discovery <unittest-test-discovery>`.  By default, this will discover tests in

any file named "test*.py" under the current working directory.

You can specify particular tests to run by supplying any number of "test

labels" to ``./manage.py test``. Each test label can be a full Python dotted