The Tempest team has put together documentation recently, available at http://docs.openstack.org/developer/tempest/.

You can use pyreverse to generate class diagram from python source. Since you are using devstack, it installs pyreverse.

I created a class diagram for network tests. Check it here.

Please do the following on devstack machine:

1. First install dot using the command

   sudo apt-get install graphviz

2. Now you can start using pyreverse. I generated the above file using the command.

   cd /opt/stack/tempest/tempest pyreverse -o png -p tempest-test-networks /network

Click here for the class diagram of nova baremetal driver. In the similar way, class diagram can be generated for any openstack class.

Hope this helps.

The sub-team working on the Neutron tests in Tempest have written a document that serves as a wonderful introduction to writing Tempest tests. It's a little focused on Neutron, but it's still useful for other parts of Tempest as well.

In particular the section "Getting to know the Tempest test framework" will be relevant. It won't give you the class diagram you're asking for, unfortunately Tempest doesn't have this (yet?), but it will give you good pointers on where to start.