Add initial all_core_tests.yml attempt

.github/workflows/all_core_tests.yml

@@ -0,0 +1,51 @@
+name: 'ALL: Run tests on current Python'
+
+on:
+  - push
+  - pull_request
+
+jobs:
+  load_constants:
+    name: Load constants
+    uses: ./.github/workflows/constants.yml
+
+  current_python_tests:
+    name: Run on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: ['ubuntu-latest', 'windows-latest']
+    if: 'github.event_name != ''push'' || github.event.pull_request.merged == false'
+    needs: load_constants
+
+    steps:
+    - name: Check out repo
+      uses: actions/checkout@v4
+
+    - name: Install Python
+      uses: actions/setup-python@v5
+      with:
+        python-version: ${{ needs.load_constants.outputs.CURRENT_PYTHON }}
+        cache: 'pip'
+        cache-dependency-path: |
+          requirements-ci.txt
+          requirements-flake8.txt
+
+    - name: Update pip
+      run: python -m pip install -U pip
+
+    - name: Install & report CI dependencies
+      run: |
+        python -m pip install -U --force-reinstall -r requirements-ci.txt
+        python --version
+        pip list
+
+    - name: Build docs
+      run: |
+        cd doc
+        make html
+        mkdir scratch
+
+    - name: Run tests & report source coverage
+      run: |
+        pytest --cov --testall --nonloc