When using bash as your shell, pytest can use argcomplete (https://argcomplete.readthedocs.org/) for auto-completion. For this argcomplete needs to be installed and enabled.
Install argcomplete using:
sudo pip install 'argcomplete>=0.5.7'
For global activation of all argcomplete enabled python applications run:
sudo activate-global-python-argcomplete
For permanent (but not global) pytest activation, use:
register-python-argcomplete py.test >> ~/.bashrc
For one-time activation of argcomplete for pytest only, use:
eval "$(register-python-argcomplete py.test)"