The main aspect: the Horizon unit tests can be quite complex for new contributors and people extending Horizon to wrap their head around. Mocking with mox, the django unit testing framework, the openstack specific parts of the testing framework, selenium, fixtures/test data handling, qunit...
This session could work as a tutorial/tips and tricks on the different testing components. Common errors being thrown and how to debug them. If people could bring up their pain points, that would also be useful.
If there is time, it would be interesting to also address the issue from another angle and think on how to improve what we have, particularly on the Selenium front which has been quite unstable.