Contributing to Nengo

Please read our general contributing guide first. The instructions below specifically apply to the nengo project.

Developer installation

If you want to change parts of Nengo, you should do a developer installation.

git clone
cd nengo
pip install -e . --user

If you are in a virtual environment, you can omit the --user flag.

How to run unit tests

Nengo contains a large test suite, which we run with pytest. In order to run these tests, install the packages required for testing with

pip install -r requirements-test.txt

You can confirm that this worked by running the whole test suite with:

py.test --pyargs nengo

Running individual tests

Tests in a specific test file can be run by calling py.test on that file. For example:

py.test nengo/tests/

will run all the tests in

Individual tests can be run using the -k EXPRESSION argument. Only tests that match the given substring expression are run. For example:

py.test nengo/tests/ -k test_circular

will run any tests with test_circular in the name, in the file

Plotting the results of tests

Many Nengo tests have the built-in ability to plot test results for easier debugging. To enable this feature, pass the --plots to py.test. For example:

py.test --plots --pyargs nengo

Plots are placed in nengo.simulator.plots in whatever directory py.test is invoked from. You can also set a different directory:

py.test --plots=path/to/plots --pyargs nengo

Getting help and other options

Information about py.test usage and Nengo-specific options can be found with:

py.test --pyargs nengo --help

Writing your own tests

When writing your own tests, please make use of custom Nengo fixtures and markers to integrate well with existing tests. See existing tests for examples, or consult:

py.test --pyargs nengo --fixtures


py.test --pyargs nengo --markers

How to build the documentation

The documentation is built with Sphinx and has a few requirements. The Python requirements are found in requirements-test.txt and requirements-docs.txt, and can be installed with pip:

pip install -r requirements-test.txt
pip install -r requirements-docs.txt

However, one additional requirement for building the IPython notebooks that we include in the documentation is Pandoc. If you use a package manager (e.g., Homebrew, apt) you should be able to install Pandoc through your package manager. Otherwise, see this page for instructions.

After you’ve installed all the requirements, run the following command from the root directory of nengo to build the documentation. It will take a few minutes, as all examples are run as part of the documentation building process.

python build_sphinx

Getting help

If you have any questions about developing Nengo or how you can best climb the learning curve that Nengo and git present, please file an issue and we’ll do our best to help you!