borntyping

Advanced Tox usage

29 Jan 2014

This article explains the Tox configuration used by several of my Python projects, which both tests the module on multiple versions of python and runs testing-related tools for style guides, static code checking and coverage reports.

The tox.ini used here is taken from Supermann, and the source can be found here.

Running pytest to find and run tests

py.test is used to discover, run and write tests. It uses tox.ini as a configuration file by default, and the two tools work very well in combination. The first two sections tell Tox to use the default Python 2.6 and 2.7 environments, to install pytest and mock as test dependancies, and to uses py.test to run the modules tests.

[tox]
envlist=py26,py27

[testenv]
commands=py.test supermann
deps=
    pytest
    mock

[pytest]
addopts=-qq --strict --tb=short

Running flake8 to check code

flake8 wraps several Python tools for static checking of code - pep8 for style, and pyflakes for static error checking. This configures it to use tox.ini for it’s configuration - reducing the number of configuration files in the repo.

[testenv:py26-flake8]
commands=flake8 --config=tox.ini supermann
basepython=python2.6
deps=flake8

[flake8]
exclude=supermann/riemann/riemann_pb2.py
max-complexity=10

Running coverage to show untouched code

Coverage is by far the most verbose tool configured in my tox.ini, but the HTML reports it generates are very useful for working out which parts of my code aren’t being run by my tests. This does several new things with tox: it runs two commands (one to generate the data, and another to render a HTML report), and uses the dependencies from the existing testenv configuration.

Coverage itself is told to use tox.ini for it’s configuration, and is configured to ingnore various parts of the codebase (the tests folder, and lines of code that should never run). The coverage files are placed in .tox to keep the repository tidy while working.

[testenv:py26-coverage]
basepython=python2.6
commands=
    coverage run --rcfile tox.ini --source supermann -m py.test
    coverage html --rcfile tox.ini
deps=
    {[testenv]deps}
    coverage

[run]
data_file=.tox/py26-coverage/data
omit=supermann/tests/*

[report]
exclude_lines=
    def __repr__
    raise NotImplementedError
    class NullHandler

[html]
title=Supermann coverage report
directory=.tox/py26-coverage

Recent Posts