---

examples/tox/mymath/__init__.py

def add(x, y):
    return x+y

examples/tox/setup.py

from setuptools import setup

setup(name='mymath',
      version='0.2',
      description='The best math library',
      url='http://github.com/szabgab/mymath',
      author='Foo Bar',
      author_email='foo@bar.com',
      license='MIT',
      packages=['mymath'],
      zip_safe=False,
      requires=[
      ],
      long_description='Long description',
      scripts=[],
      )

examples/tox/test_mymath.py

import mymath

def test_add():
    assert mymath.add(2, 3) == 5

examples/tox/tox.ini

[tox]
envlist = py38

[testenv]
deps = pytest
commands =
    pytest