[TIP] tox and coverage across multiple envs

Andrew Dalke dalke at dalkescientific.com
Wed Aug 10 00:42:40 PDT 2011

Hi Ned,

On Aug 10, 2011, at 2:32 AM, Ned Batchelder wrote:
> I don't understand what those file names are that you're showing.
> You should have gotten data files like .coverage.machine.pid.12345 .
> And then "coverage combine" should have created a single .coverage
> file from them.  I'm not familiar with tox, is there something it
> does to affect the coverage collection?

Each tox environment has a name, like "py27-oe174" or "py27-ob23svn1",
and an associated configuration. Each configuration may have
dependencies. Tox makes a virtualenv for py27-oe174 under the
directory (this includes any extra download/installs)


To run an environment, it appears that tox does a "setup.py install"
into the associated directory. For this environment the module
is put into


but for another environment it's put into


Then because of the tox "commands" setting of
  coverage run -p ./tests/unit2 discover -s tests

tox runs the environment specific "coverage".

This puts the various .coverage.machine.pid.12345 files into
my top-level directory, which I can collect.

The problem is that each tox environment has its own PYTHONPATH,
so that "from chemfp import openbabel" refers to


depending on the environment that I run. This is how tox
maintains the needed isolation.

The problem is that I want to merge those different reports
into one. In my case I can get what I want by removing


though I don't know if that's a generally useful practice.

Perhaps there's an easy way to hack the .coverage.* format?

				dalke at dalkescientific.com

More information about the testing-in-python mailing list