remove numpy and pandas from job

Author: SimonBlanke

.github/workflows/ci.yml

@@ -259,24 +259,33 @@ jobs:
       - name: Install minimal dependencies (no numpy, no scipy)
         run: |
           python -m pip install --upgrade pip
-          python -m pip install build pandas pytest tqdm
+          python -m pip install build pytest tqdm
 
       - name: Build and install package
         run: |
           python -m pip install build
           python -m build
           pip install dist/*.whl
 
-      - name: Verify numpy is NOT installed
+      - name: Uninstall numpy and pandas (test pure Python mode)
+        run: |
+          pip uninstall numpy pandas -y
+
+      - name: Verify numpy and pandas are NOT installed
         run: |
           python -c "
           import sys
-          try:
-              import numpy
-              print('ERROR: numpy is installed but should not be!')
+          errors = []
+          for mod in ('numpy', 'pandas'):
+              try:
+                  __import__(mod)
+                  errors.append(f'{mod} is installed but should not be')
+              except ImportError:
+                  print(f'OK: {mod} is not installed')
+          if errors:
+              for e in errors:
+                  print(f'ERROR: {e}')
               sys.exit(1)
-          except ImportError:
-              print('OK: numpy is not installed')
           "
 
       - name: Verify array backend uses pure Python
@@ -292,13 +301,62 @@ jobs:
         run: |
           python -m pytest tests/test_dependencies/test_no_numpy.py -v --tb=short -p no:warnings
 
+  # ===========================================================================
+  # STAGE 3d: C Extension Tests (no numpy, with compiled C backend)
+  # ===========================================================================
+  test-c-extension:
+    name: Tests (C extension, no numpy)
+    runs-on: ubuntu-latest
+    needs: api-smoke-tests
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Python 3.11
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+
+      - name: Install build dependencies
+        run: |
+          python -m pip install --upgrade pip
+          python -m pip install build pandas pytest tqdm setuptools
+
+      - name: Build and install package (with C extension)
+        run: |
+          python -m pip install build
+          python -m build
+          pip install dist/*.whl
+
+      - name: Uninstall numpy (keep C extension)
+        run: |
+          pip uninstall numpy -y || true
+
+      - name: Verify C extension is active
+        run: |
+          python -c "
+          from gradient_free_optimizers._array_backend import _backend_name, HAS_NUMPY, HAS_C_EXTENSION
+          assert not HAS_NUMPY, 'numpy should not be installed'
+          assert HAS_C_EXTENSION, 'C extension should be available'
+          assert _backend_name == 'c_extension', f'Expected c_extension backend, got {_backend_name}'
+          print('OK: using C extension array backend')
+          "
+
+      - name: Run C extension unit tests
+        run: |
+          python -m pytest tests/test_internal/test_array_backend/test_c_extension.py -v --tb=short -p no:warnings
+
+      - name: Run dependency isolation tests
+        run: |
+          python -m pytest tests/test_dependencies/test_no_numpy.py -v --tb=short -p no:warnings
+
   # ===========================================================================
   # STAGE 4: Coverage Report (only on Ubuntu with full dependencies)
   # ===========================================================================
   coverage:
     name: Coverage Report
     runs-on: ubuntu-latest
-    needs: [test-matrix, test-no-scipy, test-no-numpy]
+    needs: [test-matrix, test-no-scipy, test-no-numpy, test-c-extension]
     steps:
       - name: Checkout code
         uses: actions/checkout@v4