You need to recreate the environment and run a test rqworker, as is done in manage.py
The important thing to remember is that the rqworker needs to run with
SECUREDROP_ENV=test because it loads the config and runs some Python code independently of the test runner.
My preferred way to do this is:
vagrant up development vagrant ssh tmux # so you can monitor the output of rqworker for errors. You could also run it in the background.