Tested on:Raspberry Pi 2; Raspberry Pi B+; Python 2.7; Raspbian pre Jessie
Prerequisites:Raspberry Pi with Raspbian Jessie and internet connection (see steps 1-7 in the Introduction)

Python project setup for test-driven development

Real test-driven development (TDD: writing the tests before the code) is often impossible when programming a Raspberry Pi. For example, how should the test suite verify that triggering an rc switch with a 433Mhz Sender really happened? A very sophisticated hardware setup would be required.
It is still a good idea to practise TDD whenever possible, test everything that could be tested and to write manually executable hardware tests with comments what should happen (e.g. ‘# Running this test activates the rc switch for 10 seconds.’).

Install the test-driven setup
Boot the Raspberry Pi, then type in terminal

The installed modules

  • Pytest for running the tests
  • Coverage for code coverage measurement
  • Sphinx for documenting the project
  • IPython/IPDB for debugging
  • Use mock to simulate hardware events

Start the dummy project

Run the tests

If the installation passed, this yields one successfull and one failed test:

TDD setup failed test

TDD setup failed test

See the README.md with sudo nano ~/MyProject_tdd/README.md for more usage information.

Virtual environment
If you want to keep the dependencies bound to the application instead of a system wide installation, setup and activate a virtual environment before installing the requirements.txt with pip.

Test-driven project file structure
In addition to the files from the basic python project setup, there are some more files:

Complex file structure

Test-driven project setup

This project setup has a sample documentation build with Sphinx and is setup for test-driven development with the pytest-coverage test framework.
Test framework file structure

Test framework file structure

The additional files are

  • htmlcov: directory for storing code coverage measurement results
  • _build: stores the Sphinx html documentation
  • index.rst: main file for building the documentation in ReStructured Text format
  • MyProject/tests/test_myproject.py: sample test file
Test-driven development wiki: https://en.wikipedia.org/wiki/Test-driven_development
Home automation with rc switches: http://www.knight-of-pi.org/cheap-home-automation-with-a-raspberry-pi-controlling-rc-switches-with-pi-switch/
Coverage tutorial: http://www.knight-of-pi.org/using-coverage-on-a-raspberry-pi/
Sphinx Tutorial: http://www.knight-of-pi.org/generating-the-documentation-of-raspberry-pi-python-projects-with-sphinx/
Mock Tutorial: http://www.knight-of-pi.org/software-testing-mock-edge-values-or-physical-interactions/
Virtual environment tutorial: http://www.knight-of-pi.org/virtual-environments-simplify-project-management/
Basic python project setup: http://www.knight-of-pi.org/standard-python-project-file-setup/
IPython and IPDB primer: http://www.knight-of-pi.org/fix-your-bugs-using-the-ipyhton-debugger-ipdb-on-a-raspberry-pi/

Knight of Pi

Johannes Bergs aka Knight of Pi. Diploma in Bioinformatics, some Webdesign and Python coding then. Living in the beautiful city of Vienna.


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