Document pytest test running instruction, ability to run the tests on a dev machine

[kornpow]

Trying to run the tests for the code, I noticed that it isn't specifically documented how to run the tests.

At the moment, it also seems like the only way to run the tests is if you are on a Raspberry Pi, because of the PiCamera dep. That could be documented.

Things that might be useful:

1. Create a requirements-dev.txt which contains pytest and and other tools we may want to use. black has been suggested at times, though controversial, flake8 could be good as well.
2. Even on the RPi, and have manually installed pytest I still need to do this to run the tests PYTHONPATH=src pytest

I might try and tackle parts of this, but wanted to create an issue to remind me.

[Chaitanya-Keyal]

If I’m not mistaken, the test suite is designed to run on non-Raspberry Pi hardware as well. The documentation can be found here: /tests/README.md. There’s also a /tests/requirements.txt.

That said, I agree it would be better to consolidate this into a requirements-dev.txt and add other developer tools like linters/formatters. #715 is related to this. Personally, I’d love to see us using black.

[kornpow]

I've been getting really into the uv python package management ecosystem recently. Its been a game changer since it can manage the python environment in addition to the python installation as a whole. Its fast and works really well.

The same organization makes a tool called ruff which does linting and also formatting.
https://github.com/astral-sh/ruff

With uv we wouldn't really need any requirements.txt or requirements-dev.txt, all the dependancies are defined in pyproject.toml and can be grouped.

Ruff supports a config file, so we could potentially format it our own custom way, since I know @kdmukai wasn't a huge fan of the black formatter

[Chaitanya-Keyal]

I agree! I love uv. In fact, I just mentioned it in #808.

ruff is also pretty nice, although it’s designed to be a drop-in replacement for black. You’re right that it supports a config file, but the options are extremely limited, just like black. The available configurations are listed in their docs and imo they aren't anything we'd really want to change from the defaults.