import test infrastructure for c, c++ and python library usage

unittest/python/CMakeLists.txt

@@ -0,0 +1,40 @@
+# we must have shared libraries enabled for testing the python module
+if(NOT BUILD_SHARED_LIBS)
+  message(STATUS "Skipping Tests for the LAMMPS Python Module: must enable BUILD_SHARED_LIBS")
+  return()
+endif()
+
+if(CMAKE_VERSION VERSION_LESS 3.12)
+  find_package(PythonInterp 3.5) # Deprecated since version 3.12
+  if(PYTHONINTERP_FOUND)
+    set(Python_EXECUTABLE ${PYTHON_EXECUTABLE})
+  endif()
+else()
+  find_package(Python3 COMPONENTS Interpreter)
+endif()
+
+if (Python_EXECUTABLE)
+  # prepare to augment the environment so that the LAMMPS python module and the shared library is found.
+  set(PYTHON_TEST_ENVIRONMENT PYTHONPATH=${LAMMPS_PYTHON_DIR}:$ENV{PYTHONPATH})
+  if(APPLE)
+    list(APPEND PYTHON_TEST_ENVIRONMENT DYLD_LIBRARY_PATH=${CMAKE_BINARY_DIR}:$ENV{DYLD_LIBRARY_PATH})
+  else()
+    list(APPEND PYTHON_TEST_ENVIRONMENT LD_LIBRARY_PATH=${CMAKE_BINARY_DIR}:$ENV{LD_LIBRARY_PATH})
+  endif()
+  if(LAMMPS_MACHINE)
+    # convert from '_machine' to 'machine'
+    string(SUBSTRING ${LAMMPS_MACHINE} 1 -1 LAMMPS_MACHINE_NAME)
+    list(APPEND PYTHON_TEST_ENVIRONMENT LAMMPS_MACHINE_NAME=${LAMMPS_MACHINE_NAME})
+  endif()
+
+  add_test(NAME PythonOpen
+           COMMAND ${Python_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/python-open.py -v
+           WORKING_DIRECTORY ${EXECUTABLE_OUTPUT_PATH})
+  set_tests_properties(PythonOpen PROPERTIES ENVIRONMENT "${PYTHON_TEST_ENVIRONMENT}")
+  add_test(NAME PythonCommands
+           COMMAND ${Python_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/python-commands.py -v
+           WORKING_DIRECTORY ${EXECUTABLE_OUTPUT_PATH})
+  set_tests_properties(PythonCommands PROPERTIES ENVIRONMENT "${PYTHON_TEST_ENVIRONMENT}")
+else()
+  message(STATUS "Skipping Tests for the LAMMPS Python Module: no suitable Python interpreter")
+endif()