Test on both the oldest and latest supported Python versions.

.github/workflows/run-tests.yml

@@ -8,6 +8,9 @@ on:
 jobs:
   run-tests:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ['3.8', '3.x']
 
     steps:
       - name: Checkout
@@ -16,6 +19,11 @@ jobs:
       - name: Install dependencies
         run: pip3 install pylint mypy coverage
 
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+
       - name: Run linters
         run: |
           pylint --errors-only full_offline_backup_for_todoist
@@ -25,6 +33,7 @@ jobs:
         run: coverage run -m unittest && coverage lcov
 
       - name: Upload coverage report
+        if: ${{ matrix.python-version == '3.x' }}
         uses: coverallsapp/[email protected]
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}