Save CI resources + document why each version is covered #422

	name: Test

	on:
	push:
	branches:
	- master
	pull_request:
	workflow_dispatch:

	jobs:
	build:
	runs-on: ubuntu-latest
	strategy:
	fail-fast: false
	matrix:
	# NOTE: The idea here is:
	# - Cover both CPython and PyPy3
	# - Cover both the oldest and most recent version supported
	# - Cover switch "<3.10" on both sides at the edge, i.e. cover
	# both 3.9 (for "<"/true) and 3.10 (for ">="/false)
	# since we have a switch like that
	# (see `install_requires` in `setup.py` for details)
	# That allows us to save resources on:
	# - CPython 3.11
	python-version: ["3.8", "3.9", "3.10", "3.12", "pypy-3.8", "pypy-3.10"]

	steps:
	- uses: actions/checkout@v4

	- name: Set up Python ${{ matrix.python-version }}
	uses: actions/setup-python@v4
	with:
	python-version: ${{ matrix.python-version }}

	- name: Install project dependencies
	run: \|
	pip3 install --upgrade pip
	pip3 install codecov tox tox-gh-actions

	- name: Run online tests with tox
	run: tox -- -m online

	- name: Run offline tests with tox with no access to the Internet
	run: \|
	# We're using unshare to take Internet access
	# away from tox so that we'll notice whenever some new test
	# is missing @pytest.mark.online decoration in the future
	unshare --map-root-user --net -- \
	sh -c 'ip link set lo up; tox -- -m "not online"'

	- name: Run coverage
	run: codecov

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