docs: Add instructions for testing logging.

Author: dianakhuang

docs/testing_and_debugging.rst

@@ -65,3 +65,15 @@ so that you maintain your command history:
 
 
 .. _edx-platform testing documentation: https://docs.openedx.org/projects/edx-platform/en/latest/concepts/testing/testing.html#running-python-unit-tests
+
+Custom Logging Testing
+----------------------
+
+If you would like to test modifications to the docker logging configuration as
+listed in the custom-created `public-dockerfiles logging configuration`_, this
+file won't exist in devstack due to the local edx-platform copy overriding it.
+
+Any changes will need to be copied over into ``/py_configuration_files/(lms|cms).py`` to be tested
+on devstack.
+
+:: _public-dockerfiles logging configuration:https://github.com/edx/public-dockerfiles/blob/main/dockerfiles/edx-platform.Dockerfile#L262-L264