Fixed #17365, #17366, #18727 -- Switched to discovery test runner.

Thanks to Preston Timmons for the bulk of the work on the patch, especially
updating Django's own test suite to comply with the requirements of the new
runner. Thanks also to Jannis Leidel and Mahdi Yusuf for earlier work on the
patch and the discovery runner.

Refs #11077, #17032, and #18670.

docs/releases/1.6.txt

@@ -69,6 +69,29 @@ This avoids the overhead of re-establishing a connection at the beginning of
 each request. For backwards compatibility, this feature is disabled by
 default. See :ref:`persistent-database-connections` for details.
 
+Discovery of tests in any test module
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Django 1.6 ships with a new test runner that allows more flexibility in the
+location of tests. The previous runner
+(``django.test.simple.DjangoTestSuiteRunner``) found tests only in the
+``models.py`` and ``tests.py`` modules of a Python package in
+:setting:`INSTALLED_APPS`.
+
+The new runner (``django.test.runner.DjangoTestDiscoverRunner``) uses the test
+discovery features built into unittest2 (the version of unittest in the Python
+2.7+ standard library, and bundled with Django). With test discovery, tests can
+be located in any module whose name matches the pattern ``test*.py``.
+
+In addition, the test labels provided to ``./manage.py test`` to nominate
+specific tests to run must now be full Python dotted paths (or directory
+paths), rather than ``applabel.TestCase.test_method_name`` pseudo-paths. This
+allows running tests located anywhere in your codebase, rather than only in
+:setting:`INSTALLED_APPS`. For more details, see :doc:`/topics/testing/index`.
+
+This change is backwards-incompatible; see the :ref:`backwards-incompatibility
+notes<new-test-runner>`.
+
 Time zone aware aggregation
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
@@ -238,6 +261,40 @@ In previous versions, database-level autocommit was only an option for
 PostgreSQL, and it was disabled by default. This option is now :ref:`ignored
 <postgresql-autocommit-mode>` and can be removed.
 
+.. _new-test-runner:
+
+New test runner
+~~~~~~~~~~~~~~~
+
+In order to maintain greater consistency with Python's unittest module, the new
+test runner (``django.test.runner.DiscoverRunner``) does not automatically
+support some types of tests that were supported by the previous runner:
+
+* Tests in ``models.py`` and ``tests/__init__.py`` files will no longer be
+  found and run. Move them to a file whose name begins with ``test``.
+
+* Doctests will no longer be automatically discovered. To integrate doctests in
+  your test suite, follow the `recommendations in the Python documentation`_.
+
+Django bundles a modified version of the :mod:`doctest` module from the Python
+standard library (in ``django.test._doctest``) in order to allow passing in a
+custom ``DocTestRunner`` when instantiating a ``DocTestSuite``, and includes
+some additional doctest utilities (``django.test.testcases.DocTestRunner``
+turns on the ``ELLIPSIS`` option by default, and
+``django.test.testcases.OutputChecker`` provides better matching of XML, JSON,
+and numeric data types).
+
+These utilities are deprecated and will be removed in Django 1.8; doctest
+suites should be updated to work with the standard library's doctest module (or
+converted to unittest-compatible tests).
+
+If you wish to delay updates to your test suite, you can set your
+:setting:`TEST_RUNNER` setting to ``django.test.simple.DjangoTestSuiteRunner``
+to fully restore the old test behavior. ``DjangoTestSuiteRunner`` is
+deprecated but will not be removed from Django until version 1.8.
+
+.. _recommendations in the Python documentation: http://docs.python.org/2/library/doctest.html#unittest-api
+
 Addition of ``QuerySet.datetimes()``
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~