👷 Add pytest GH workflow.

.github/workflows/test.yaml

@@ -0,0 +1,86 @@
+name: Test
+
+on:
+- push
+
+concurrency:
+  group: tests-${{ github.head_ref || github.ref }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
+jobs:
+  tests:
+    name: ${{ matrix.os }} / ${{ matrix.python-version }}
+    runs-on: ${{ matrix.image }}
+    strategy:
+      matrix:
+        os:
+        - Ubuntu
+        - macOS
+        - Windows
+        python-version:
+        - "3.8"
+        - "3.9"
+        - "3.10"
+        - "3.11"
+        - "3.12"
+        include:
+          - os: Ubuntu
+            image: ubuntu-latest
+          - os: Windows
+            image: windows-latest
+          - os: macOS
+            image: macos-latest
+      fail-fast: false
+    defaults:
+      run:
+        shell: bash
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v4
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Bootstrap poetry
+        run: |
+          curl -sL https://install.python-poetry.org | python - -y
+
+      - name: Update PATH
+        if: ${{ matrix.os != 'Windows' }}
+        run: echo "$HOME/.local/bin" >> $GITHUB_PATH
+
+      - name: Update Path for Windows
+        if: ${{ matrix.os == 'Windows' }}
+        run: echo "$APPDATA\Python\Scripts" >> $GITHUB_PATH
+
+      - name: Configure poetry
+        run: |
+          poetry config virtualenvs.in-project true
+
+      - name: Set up cache
+        uses: actions/cache@v3
+        id: cache
+        with:
+          path: .venv
+          key: venv-${{ runner.os }}-${{ steps.full-python-version.outputs.version }}-${{ hashFiles('**/poetry.lock') }}
+
+      - name: Ensure cache is healthy
+        if: steps.cache.outputs.cache-hit == 'true'
+        run: |
+          # `timeout` is not available on macOS, so we define a custom function.
+          [ "$(command -v timeout)" ] || function timeout() { perl -e 'alarm shift; exec @ARGV' "$@"; }
+
+          # Using `timeout` is a safeguard against the Poetry command hanging for some reason.
+          timeout 10s poetry run pip --version || rm -rf .venv
+
+      - name: Check lock file
+        run: poetry lock --check
+
+      - name: Install dependencies
+        run: poetry install --all-extras --with=dev
+
+      - name: Run pytest
+        run: poetry run pytest -s