TST: add configuration for no-network tests

.github/workflows/ci-testing.yml

@@ -13,10 +13,16 @@ jobs:
         os: [ubuntu-latest, macos-latest, windows-latest]
         python-version: [3.9, '3.10', '3.11', '3.12']
         shapely-dev: [false]
+        no-network: [false]
         include:
           - os: ubuntu-latest
             python-version: '3.11'
             shapely-dev: true
+            no-network: false
+          - os: ubuntu-latest
+            python-version: '3.11'
+            shapely-dev: false
+            no-network: true
 
     steps:
       - uses: actions/checkout@v4
@@ -68,6 +74,7 @@ jobs:
 
       - name: Testing
         id: test
+        if: ${{ ! matrix.no-network }}
         # we need to force bash to use line continuations on Windows
         shell: bash
         run: |
@@ -82,6 +89,14 @@ jobs:
               --mpl-results-path="cartopy_test_output-${{ matrix.os }}-${{ matrix.python-version }}-${{ matrix.shapely-dev }}" \
               --pyargs cartopy ${EXTRA_TEST_ARGS}
 
+      - name: No Network Tests
+        if: matrix.no-network
+        run: |
+          pip install pytest-socket
+          pytest -rfEsX -n 4 \
+              --color=yes \
+              --pyargs cartopy -m "not natural_earth and not network" --disable-socket
+
       - name: Coveralls
         if: steps.coverage.conclusion == 'success'
         env: