Fixed broken import in typecaster.h (#1181)

- Fixed the broken import _slsdet --> slsdet._slsdet caused by a previous upgrade
- Added tests that exercises the conversion from python to C++ and from C++ to python
- Python unit tests now run in CI (!)

.github/workflows/cmake.yaml

@@ -14,7 +14,13 @@ jobs:
     runs-on: ubuntu-latest
     name: Configure and build using cmake
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: 3.12
+          cache: 'pip'
+      - run: pip install pytest numpy
+
       - uses: awalsh128/cache-apt-pkgs-action@latest
         with:
           packages: libhdf5-dev qtbase5-dev qt5-qmake libqt5svg5-dev libpng-dev libtiff-dev
@@ -27,12 +33,15 @@ jobs:
 
       - name: Build
         # Build your program with the given configuration
-        run: cmake --build ${{github.workspace}}/build -j2 --config ${{env.BUILD_TYPE}}
+        run: cmake --build ${{github.workspace}}/build -j4 --config ${{env.BUILD_TYPE}}
 
-      - name: Test
+      - name: C++ unit tests
         working-directory: ${{github.workspace}}/build
-        # Execute tests defined by the CMake configuration.
-        # See https://cmake.org/cmake/help/latest/manual/ctest.1.html for more detail
         run: ctest -C ${{env.BUILD_TYPE}} -j1
 
+      - name: Python unit tests
+        working-directory: ${{github.workspace}}/build/bin
+        run: |
+          python -m pytest ${{github.workspace}}/python/tests
+