Index: docs/contributing.txt
===================================================================
--- docs/contributing.txt	(revision 6282)
+++ docs/contributing.txt	(working copy)
@@ -652,13 +652,30 @@
 Yes, the unit tests need a settings module, but only for database connection
 info, with the ``DATABASE_ENGINE`` setting. You will also need a ``ROOT_URLCONF``
 setting (its value is ignored; it just needs to be present) and a ``SITE_ID``
-setting (any non-zero integer value will do) in order for all the tests to pass.
+setting (any non-zero integer value will do) in order for all the
+tests to pass.
 
-The unit tests will not touch your existing databases; they create a new
-database, called ``django_test_db``, which is deleted when the tests are
+If you use the ``sqlite3`` database engine, no further settings are needed and a
+temporary database will be created in memory when running the tests.
+
+For other backends, the ``DATABASE_USER`` setting needs to specify an existing
+user account for the database engine. The ``DATABASE_NAME`` setting must be the
+name of an existing database to which the given user has permission to connect.
+The unit tests will not touch that database; they create a new database which
+has the same name prefixed with ``test_``, and it is deleted when the tests are
 finished. This means your user account needs permission to execute ``CREATE
 DATABASE``.
 
+To run a subset of the unit tests, append the names of the test modules to the
+``runtests.py`` command line. See the list of directories in
+``tests/modeltests`` and ``tests/regressiontests`` for module names.
+
+As an example, if Django is not in your ``PYTHONPATH``, you placed
+``settings.py`` in the ``tests/`` directory, and you'd like to only run tests
+for generic relations and internationalization, type::
+
+    PYTHONPATH=.. ./runtests.py --settings=settings generic_relations i18n
+
 Requesting features
 ===================