For testing you have to install tox, either system-wide via your distribution’s package manager, e.g. on debian/Ubuntu with:

$ sudo apt-get install python-tox

or via pip:

$ sudo pip install tox

Run the tests via tox for all Python versions configured in tox.ini:

$ tox

If you want to test only against your default Python version, just run:

$ make test

or activate the virtualenv and run:

$ poetry shell
$ pytest -v

To see all available make target just run make without arguments.