Test Sphinx's master branch distinctly from ordinary tests

Author: AA-Turner

.github/workflows/test.yml

@@ -41,6 +41,23 @@ jobs:
         if: "endsWith(matrix.python, '-dev')"
         with:
           python-version: ${{ matrix.python }}
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          python -m pip install .[test]
+
+      - name: Test with pytest
+        run: python -m pytest --durations 25
+
+  test-latest-sphinx:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+      - name: Set up Python ${{ matrix.python }}
+        uses: actions/setup-python@v4
+        with:
+          python-version: "3"
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip