Initial GH workflow for running cpython tests

Add coverage output

Reduce dependencies

add numpy

.github/workflows/ci.yml

@@ -67,6 +67,33 @@ jobs:
           cd tests
           python -m vcztools --help
 
+  c_python_test:
+    name: CPython interface tests
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+      - name: Install system dependencies
+        run: |
+          sudo apt install -y gcovr
+      - name: Install python dependencies
+        run: |
+          python -m pip install --upgrade pip
+          python -m pip install numpy pytest
+      - name: Build module with coverage
+        run: |
+          # Build the extension module in-place so pytest can find it
+          CFLAGS="--coverage" python3 setup.py build_ext --inplace
+      - name: Run tests
+        run: |
+          pytest -vs tests/test_cpython_interface.py
+      - name: Show coverage
+        run: |
+          gcovr --filter vcztools
+
   c_test:
     name: C tests
     runs-on: ubuntu-latest
@@ -88,7 +115,7 @@ jobs:
         run: |
           ninja -C build coverage-text
           cat build/meson-logs/coverage.txt
-      - name: Valgrind 
+      - name: Valgrind
         working-directory: ./lib
         run: |
           valgrind --leak-check=full --error-exitcode=1 ./build/tests