Add a note about testing to the README

README.rst

@@ -69,6 +69,9 @@ Table of Contents
   - `Logging predicate evaluation`_
 
 - `Best practices`_
+
+  - `Testing`_
+
 - `API Reference`_
 - `Licence`_
 
@@ -722,6 +725,21 @@ have ``rules`` do so, just edit your ``INSTALLED_APPS`` setting:
     from __future__ import absolute_import
 
 
+Testing
+-------
+
+When using Django's built in `TestClient` using the `force_login` method will
+fail unless you specify a specific authentication backend in Django versions
+up to 1.10.
+
+To work around this pass ``django.contrib.auth.backends.ModelBackend`` as the
+``backend`` argument:
+
+.. code:: python
+
+    client.force_login(user, backend='django.contrib.auth.backends.ModelBackend')
+
+
 API Reference
 =============