Running tests

The BlenderBIM Add-on has three layers of tests for each of its three technology layers:

  1. Core tests: abstract domain logic unit tests agnostic of Blender

  2. Tool tests: low-level concrete unit tests dependent on Blender

  3. BIM tests: high-level integration UI and smoke tests dependent on Blender

These tests use pytest as the test framework and runner, so install it:

pip install pytest

All development is expected to use test driven development, and so we expect test coverage to be 100% where it is technically possible to test.

When running tests, Makefile targets are provided for convenience so you can type in a simple command without knowing the internals. This means you can run tests by using the make command.

Because the BlenderBIM Add-on depends on IfcOpenShell, it is advised to also run tests for IfcOpenShell and its Python bindings, which is not covered in this document.

Core tests

The core layer tests are pure Python unit tests with no dependencies on Blender or other modules. They are designed to be fast and easy to run as they test purely abstract domain logic.

Although they are vanilla Python tests, they do not use the Python Mock module. Instead, a lightweight Prophecy mocker class is used, which allows tests to be written in a highly concise, expressive manner. For those coming from a BDD background in Ruby’s RSpec, PHP’s PHPSpec, and PHP’s Prophecy, this is very similar.

cd src/blenderbim/
make test-core
# If you're on Windows, and don't want to use make, use:
pytest -p no:pytest-blender test/core

Tool tests

The tool layer tests actual concrete functions. You will need to install the following dependencies:

  • pytest-blender, accessible to your system’s Python

  • Blender executable, accessible to pytest-blender on your system’s Python (e.g. through the blender command in your path)

pip install pytest-blender
# Check that "Blender" is in your system's path

On Windows, you can add Blender to the system path by doing:

  1. Open the start menu and launch Control Panel > System > Edit the system environment variables

  2. In the System Properties window, under the Advanced tab press Environment Variables. This will open a dialog showing a list of all your variables.

  3. In the System Variables section select the entry named Path, and press Edit…. This will open a new dialog showing all the directories stored in the Path variable.

  4. Press New and browse to the directory where your blender.exe is located, such as in C:\Program Files\Blender Foundation\Blender 3.2.

In addition, you will need to install these dependencies for Blender:

  • pytest, accessible to your Blender Python

  • pytest-bdd, accessible to your Blender Python

You can install the dependencies by running the script in Blender:

  1. Launch Blender

  2. Load src/blenderbim/scripts/ in the Blender text editor

  3. Run the script by pressing Text > Run Script.

  4. Check the Blender console for any errors or success messages.


The scripts/ may not work for all operating systems and installation environments. In this case, you may be required to install the dependencies manually.

Please be aware that some Blender may come packaged with its own Python, which may be separate to the Python installation on your system. Be sure to install the dependencies to the correct Python environment.

Then, run the tests. This will launch Blender headlessly and check the behaviour of all concrete functions.

cd src/blenderbim/
make test-tool # Test everything
make test-tool MODULE=foo # Only test a single module
# If you're on Windows, and don't want to use make, use:
pytest test/tool # Test everything
pytest test/tool/ # Only test a single module

BlenderBIM Add-on tests

The BIM layer acts as a full integration test. It is not possible to fully test the UI, as we cannot reliably emit interface signals, nor read the interface as a DOM of sorts. The best we can do is to call Blender operators as a smoke test, and also check simple property and scene changes.

Before running these tests, follow the instructions for running tool tests above.

You will also need to enable the Sun Position add-on, as it is required to test georeferencing features: Edit > Preferences > Add-ons and enable Lighting: Sun Position.

cd src/blenderbim/
make test-bim # Test everything
make test-bim MODULE=foo # Only test a single module
# If you're on Windows, and don't want to use make, use:
pytest test/bim # Test everything
pytest test/bim -m "foo" ./ --maxfail=1 # Only test a single module