Updated tests to work properly for pip validation

Author: jski

.github/workflows/build.yml

@@ -221,6 +221,10 @@ jobs:
         run: |
           docker run --rm ghcr.io/${{ github.repository_owner }}/python-container-builder:${{ matrix.python_version }}-${{ github.sha }} pdm --version
 
+      - name: Test pip is installed in venv
+        run: |
+          docker run --rm ghcr.io/${{ github.repository_owner }}/python-container-builder:${{ matrix.python_version }}-${{ github.sha }} /.venv/bin/pip --version
+
       - name: Test venv is created
         run: |
           docker run --rm ghcr.io/${{ github.repository_owner }}/python-container-builder:${{ matrix.python_version }}-${{ github.sha }} sh -c 'test -d /.venv && echo "venv exists"'