nose-multiversion /

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NoseMultiVersion is a Nose plugin to run tests simultaneously in different versions of Python.

When the plugin is activated, your test suite spawns off subprocesses to run the same tests in each Python interpreter then the results are printed in the main process. It was designed for libraries or applications that want to support legacy versions of Python or for projects that need to work in virtual environments that are configured differently. Because it uses sockets via execnet and parallel subprocesses, it only adds minimal overhead to your test time.


NoseMultiVersion, Nose, and execnet must be installed in each version of Python you want to run your tests in. Your test and application modules do not need to be installed in each Python version.

Here's how to install the NoseMultiVersion and its dependencies:

Install With Pip From Source

Grab the pip source and do something like this:

$ cd /pip/source
$ sudo python2.4 ./scripts/pip install -e hg+
$ sudo python2.5 ./scripts/pip install -e hg+
$ sudo python2.6 ./scripts/pip install -e hg+

Install With Pip From PyPI

Just like above but do:

$ cd /pip/source
$ sudo python2.4 ./scripts/pip install NoseMultiVersion
$ sudo python2.5 ./scripts/pip install NoseMultiVersion
$ sudo python2.6 ./scripts/pip install NoseMultiVersion

Install With Setuptools

$ sudo easy_install-2.4
$ sudo easy_install-2.5
$ sudo easy_install-2.6

Run A Simple Test Suite In Multiple Versions of Python

If you have an application without many dependencies you can probably just run the tests in multiple versions like this:

$ cd /your/test/suite
$ nosetests --in-python=2.4,2.5,2.6

Run A Complex Test Suite In A Virtualenv

It's most likely that your application has some dependencies that you are probably managing with a custom virtualenv. The value passed to the --in-python= option can also be an absolute path to a Python interpreter so set up your virtualenv directories then run your tests like this:

$ cd /your/test/suite
$ nosetests --in-python=/path/to/a/virtualenv-for-2.5/bin/python --in-python=/path/to/a/virtualenv-for-2.6/bin/python

Declare Option Values in a Config Script

As with any Nose option, you can use a config file to set its value, like this:



This plugin was created by Kumar McMillan <>. Big thanks to Holger Krekel for extracting execnet into its own package. This allowed Nose to steal a nice feature from py.test :)

Bugs, Patches

Submit all bugs and patches to -- thanks!

Random Notes

  • If another plugin tries to do a frame hack then it might break because tracebacks and frames are flattened then pickled so they can be sent from a worker to the main process.
  • When Nose supports Python 3.0 as well as execnet then adding 3.0 to your options should just magically work!
  • There are probably some other nifty things to steal from py.test like decorators that raise Nose's SkipTest exception when you don't want to run a test in a specific version.