diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ef3aa8e..1065b60 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -7,8 +7,8 @@ on:
       - main
 
 jobs:
-  test:
-    name: Test
+  python_test:
+    name: Python tests
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
@@ -42,30 +42,32 @@ jobs:
         run: |
           pytest
 
-  packaging:
-    name: Packaging
+  c_python_test:
+    name: CPython interface tests
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-python@v5
+      - name: Set up Python
+        uses: actions/setup-python@v5
         with:
           python-version: '3.11'
-      - name: Install dependencies
+      - 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 build twine validate-pyproject[all]
-      - name: Check and install package
+          python -m pip install numpy pytest
+      - name: Build module with coverage
         run: |
-          validate-pyproject pyproject.toml
-          python -m build
-          python -m twine check --strict dist/*
-          python -m pip install dist/*.whl
-      - name: Check vcztools CLI
+          # Build the extension module in-place so pytest can find it
+          CFLAGS="--coverage" python3 setup.py build_ext --inplace
+      - name: Run tests
         run: |
-          vcztools --help
-          # Make sure we don't have ``vcztools`` in the CWD
-          cd tests
-          python -m vcztools --help
+          pytest -vs tests/test_cpython_interface.py
+      - name: Show coverage
+        run: |
+          gcovr --filter vcztools
 
   c_test:
     name: C tests
@@ -88,7 +90,33 @@ 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
+
+  packaging:
+    name: Packaging
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          python -m pip install build twine validate-pyproject[all]
+      - name: Check and install package
+        run: |
+          validate-pyproject pyproject.toml
+          python -m build
+          python -m twine check --strict dist/*
+          python -m pip install dist/*.whl
+      - name: Check vcztools CLI
+        run: |
+          vcztools --help
+          # Make sure we don't have ``vcztools`` in the CWD
+          cd tests
+          python -m vcztools --help
+