Easy testing with Travis and tox

I love tox – it’s a great tool for checking that your Python packages are installable, and that you support all the various configurations of Python versions and other package versions that you think you do.

It’s also quite a neat way of checking your documentation builds properly, and that your code remains PEP 8 compliant1.

I also love Travis, since it helps me accomplish much the same thing as tox, but does so in an automated way, with every push.

A typical tox.ini file for one of my projects looks a bit like this:

[tox]
envlist = py33-1.6.X,docs,flake8

[testenv]
commands=python setup.py test

[testenv:py33-1.6.X]
basepython = python3.3
deps = https://www.djangoproject.com/download/1.6b1/tarball/

# Omitted for brevity

[testenv:docs]
basepython=python
changedir=docs
deps=sphinx
commands=
sphinx-build -W -b html -d {envtmpdir}/doctrees . {envtmpdir}/html

[testenv:flake8]
basepython=python
deps=flake8
commands=
flake8 djohno

Whilst my .travis.yml file looks a bit like this:

language: python
python: 2.7
env:
 - TOX_ENV=py33-1.6.X
 - TOX_ENV=py33-1.5.X
 - TOX_ENV=py27-1.6.X
 - TOX_ENV=py27-1.5.X
 - TOX_ENV=py27-1.4.X
 - TOX_ENV=py26-1.5.X
 - TOX_ENV=py26-1.4.X
 - TOX_ENV=docs
 - TOX_ENV=flake8
install:
 - pip install tox
script:
 - tox -e $TOX_ENV

This .travis.yml file sets up an individual build job for each environment I want to test with, which makes for slightly faster builds (because they’re parallelised), and for clearer build errors (since the build status table will have red rows just for whichever jobs failed).

However, it repeats a section (the list of available environments) from my tox.ini file, which is sad. I could get around this by giving up having individual build jobs, or by just saying that I’ll fix the file when I add an environment to tox to test.

Or, I could write a little script to generate a .travis.yml file from a tox.ini file, like this:

from tox._config import parseconfig

print "language: python"
print "python: 2.7"
print "env:"
for env in parseconfig(None, 'tox').envlist:
print " - TOX_ENV=%s" % env
print "install:"
print " - pip install tox"
print "script:"
print " - tox -e $TOX_ENV"

You could even set this up to run in a git pre-commit hook or something (piping the output to .travis.yml), but that’s a job for another day.

  1.  I use flake8 for the PEP 8 checking, since it also picks up things like unused variables and imports, which is handy.

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