ci(tests): Use poetry cache action

[tony]

Potential bug (as of actions/setup-python v3.1):

Filed a report here: actions/setup-python#374, reproduction: https://github.com/tony/setup-python-poetry-version-example

The workaround for now is to use poetry env use <python-version> before poetry install

Original message

As of yesterday, @actions/setup-python@v3 supports this via v3.1.0: Release, Tag, actions/setup-python#281

steps:
- uses: actions/checkout@v3
- name: Install poetry
  run: pipx install poetry
- uses: actions/setup-python@v3
  with:
    python-version: '3.9'
    cache: 'poetry'
- run: poetry install
- run: poetry run pytest

See also: python-poetry/poetry#4205

[codecov]

Codecov Report

Merging #316 (3a68636) into master (623a393) will not change coverage.
The diff coverage is n/a.

❗ Current head 3a68636 differs from pull request most recent head 601ffef. Consider uploading reports for the commit 601ffef to get more accurate results

@@           Coverage Diff           @@
##           master     #316   +/-   ##
=======================================
  Coverage   86.80%   86.80%           
=======================================
  Files          15       15           
  Lines         879      879           
=======================================
  Hits          763      763           
  Misses        116      116           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 623a393...601ffef. Read the comment docs.

[tony]

Update (as of actions/setup-python):

When I do this, I've found I had to run poetry env ${{ matrix.python-version }} before poetry install or else it'd use the default python version:

name: tests

on: [push]

jobs:
  build:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        python-version: [ '3.10' ]
    steps:
      - uses: actions/checkout@v3
      - name: Install poetry
        run: |
          curl -O -sSL https://install.python-poetry.org/install-poetry.py
          python install-poetry.py -y --version 1.1.12
          echo "PATH=${HOME}/.poetry/bin:${PATH}" >> $GITHUB_ENV
          rm install-poetry.py

      - name: Set up Python ${{ matrix.python-version }}
        uses: actions/setup-python@v3
        with:
          python-version: ${{ matrix.python-version }}
          cache: 'poetry'

      - name: Install dependencies
        run: |
          # This is required to do as of @actions/checkout@v3 to prevent default action python (3.8) from being used
          poetry env use ${{ matrix.python-version }}
          poetry install

      - name: Lint with flake8
        run: poetry run flake8

      - name: Print python versions
        run: |
          python -V
          poetry run python -V

      - name: Test with pytest
        run: poetry run py.test