docs: Add initial notes on development guidelines

Signed-off-by: Ivan Kanakarakis <[email protected]>

Author: c00kiemon5ter

DEVELOPERS.md

@@ -1,12 +1,102 @@
 # Developing guidelines
 
-## Development Setup
+If you already cloned the repository and you know that you need to deep dive in the code,
+here are some guidelines to set up your environment.
+
+
+## Development environment setup
+
+### Python versions
+
+To manage multiple Python versions on my system, I use [`pyenv`].
+See the `pyenv` documentation on how to install and configure the tool.
+
+Install the supported python versions and enable them for this project:
+
+```shell
+$ for v in 3.6 3.7 3.8 3.9 3.10; do pyenv install "${v}:latest"; done
+$ pyenv versions --bare | xargs pyenv local
+```
+
+
+### Dependencies
+
+This project uses [`poetry`] to manage dependencies and virtual environments.
+See `poetry`'s [installation instructions] on how to install `poetry` on your system.
+
+I have opted to use [`pipx`] to install and manage `poerty` itself.
+I also use `pipx` to manage other python executables that I want readily available on my system.
+
+Once `poetry` is available on your system, install the development dependencies:
+
+```shell
+$ poetry install --with dev,test,coverage,docs --sync
+```
+
+A virtual environment will be created automatically by `poetry`.
+To enter a shell with the virtual environment loaded use the `shell` command:
+
+```shell
+$ poetry shell
+```
+
+Note that `poetry` doesn't need you to load the virtual environment.
+It will automatically load the virtual environment as you interact with the `poetry` commands.
+
 
 ## Running Tests
 
+The tests are written with the [`pytest`] test framework.
+To run the tests invoke `pytest` through `poetry`:
+
+```shell
+$ poetry run pytest
+```
+
+However, the above will only run the tests for the latest python version.
+To test all python versions invoke the test runner [`tox`]:
+
+```shell
+$ poetry run tox
+```
+
+This works because different python versions were made available through `pyenv`.
+
+
 ## Coding Rules
 
+Coding style is encoded through the configurations of [`black`] and [`isort`].
+To enforce the rules run:
+
+```shell
+$ poetry run black src/ tests/ example/
+$ poetry run isort src/ tests/ example/
+```
+
+Additional rules and suggestions are generated by [`flake8`].
+Check your code with:
+
+```shell
+$ poetry run flake8 src/
+```
+
+
 ## Commit Message Guidelines
 
+(TODO)
+
+
 ## Writing Documentation
 
+(TODO)
+
+
+  [`poetry`]: https://python-poetry.org/
+  [installation instructions]: https://python-poetry.org/docs/#installation
+  [`pipx`]: https://pypa.github.io/pipx/
+  [`pyenv`]: https://github.com/pyenv/pyenv
+  [`pytest`]: https://docs.pytest.org/
+  [`tox`]: https://tox.wiki/
+  [`black`]: https://black.readthedocs.io/
+  [`isort`]: https://pycqa.github.io/isort/
+  [`flake8`]: https://flake8.pycqa.org/