ci: test on multiple Python versions.

Author: cursoragent

.github/workflows/tests.yml

@@ -7,11 +7,15 @@ on:
 jobs:
   pytest:
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ['3.9', '3.11']
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: '3.11'
+          python-version: ${{ matrix.python-version }}
       - name: Install
         run: |
           python -m pip install --upgrade pip