Setting Up a Development Environment

This page describes how to setup a working Python development environment that can be used in developing Tacker on Ubuntu, Fedora or Mac OS X. These instructions assume you’re already familiar with Git and Gerrit, which is a code repository mirror and code review toolset , however if you aren’t please see this Git tutorial for an introduction to using Git and this guide for a tutorial on using Gerrit and Git for code contribution to Openstack projects.

If you want to be able to run Tacker in a full OpenStack environment, you can use the excellent DevStack project to do so. There is a wiki page that describes setting up Tacker using DevStack.

Getting the code

Grab the code:

git clone git://
cd tacker

Testing Tacker


The unit tests are meant to cover as much code as possible and should be executed without the service running. They are designed to test the various pieces of the tacker tree to make sure any new changes don’t break existing functionality.

The functional tests are intended to validate actual system interaction. Mocks should be used sparingly, if at all. Care should be taken to ensure that existing system resources are not modified and that resources created in tests are properly cleaned up.

Development process

It is expected that any new changes that are proposed for merge come with tests for that feature or code area. Ideally any bugs fixes that are submitted also have tests to prove that they stay fixed! In addition, before proposing for merge, all of the current tests should be passing.

Running unit tests

There are three mechanisms for running tests:, tox, and nose. Before submitting a patch for review you should always ensure all test pass; a tox run is triggered by the jenkins gate executed on gerrit for each patch pushed for review.

With these mechanisms you can either run the tests in the standard environment or create a virtual environment to run them in.

By default after running all of the tests, any pep8 errors found in the tree will be reported.

Note that the tests can use a database, see tools/ on how the databases are set up in the OpenStack CI environment.


You can use the script in the root source directory to execute tests in a virtualenv:

./ -V

With nose

You can use nose to run individual tests, as well as use for debugging portions of your code:

source .venv/bin/activate
pip install nose

There are disadvantages to running Nose - the tests are run sequentially, so race condition bugs will not be triggered, and the full test suite will take significantly longer than tox & testr. The upside is that testr has some rough edges when it comes to diagnosing errors and failures, and there is no easy way to set a breakpoint in the Tacker code, and enter an interactive debugging session while using testr.

With tox

Tacker, like other OpenStack projects, uses tox for managing the virtual environments for running test cases. It uses Testr for managing the running of the test cases.

Tox handles the creation of a series of virtualenvs that target specific versions of Python (2.7, 3.4, etc).

Testr handles the parallel execution of series of test cases as well as the tracking of long-running tests and other things.

Running unit tests is as easy as executing this in the root directory of the Tacker source code:


For more information on the standard Tox-based test infrastructure used by OpenStack and how to do some common test/debugging procedures with Testr, see this wiki page:

Running individual tests

For running individual test modules or cases, you just need to pass the dot-separated path to the module you want as an argument to it.

For executing a specific test case, specify the name of the test case class separating it from the module path with a colon.

For example, the following would run only the TestVNFMPlugin tests from tacker/tests/unit/vm/

$ ./ tacker.tests.unit.vm.test_plugin:TestVNFMPlugin


$ ./tox tacker.tests.unit.vm.test_plugin:TestVNFMPlugin

Adding more tests

Tacker has a fast growing code base and there is plenty of areas that need to be covered by unit and functional tests.

To get a grasp of the areas where tests are needed, you can check current coverage by running:

$ ./ -c


By default, calls to pdb.set_trace() will be ignored when tests are run. For pdb statements to work, invoke run_tests as follows:

$ ./ -d [test module path]

It’s possible to debug tests in a tox environment:

$ tox -e venv -- python -m [test module path]

Tox-created virtual environments (venv’s) can also be activated after a tox run and reused for debugging:

$ tox -e venv
$ . .tox/venv/bin/activate
$ python -m [test module path]

Tox packages and installs the tacker source tree in a given venv on every invocation, but if modifications need to be made between invocation (e.g. adding more pdb statements), it is recommended that the source tree be installed in the venv in editable mode:

# run this only after activating the venv
$ pip install --editable .

Editable mode ensures that changes made to the source tree are automatically reflected in the venv, and that such changes are not overwritten during the next tox run.

Post-mortem debugging

Setting OS_POST_MORTEM_DEBUG=1 in the shell environment will ensure that pdb.post_mortem() will be invoked on test failure:

$ OS_POST_MORTEM_DEBUG=1 ./ -d [test module path]