Configuration - Add support for Google Test framework in CMake #443

Enhance Google Test integration and add support for test projects.
Each Toolkit have GTests folder with place for new tests.
For adding new tests needs to extend FILES.cmake files in each GTests folder.
The single executable is created for each toolkit with all tests.
The tests grouped by module and toolkit with :: as separator.
Added option to download GTest by Cmake if not found.
Add GTest for PLib_JacobiPolynomial with comprehensive test cases
Add GTest for TCollection_AsciiString and TCollection_ExtendedString
Set C++ standard to C++14 for GTest compatibility if required

CMakeLists.txt

@@ -82,6 +82,12 @@ elseif ("${BUILD_CPP_STANDARD}" STREQUAL "C++23")
 else ()
   message (FATAL_ERROR, "misprint in c++ standard name")
 endif()
+
+if (DEFINED BUILD_GTEST AND BUILD_GTEST AND CMAKE_CXX_STANDARD LESS 14)
+  set (CMAKE_CXX_STANDARD 14)
+  message (STATUS "Info: C++14 standard is required for GTest. Set to C++14.")
+endif()
+
 set (CMAKE_CXX_STANDARD_REQUIRED ON)
 
 # include cmake file
@@ -449,6 +455,10 @@ else()
   OCCT_CHECK_AND_UNSET (USE_VTK)
 endif()
 
+if (NOT DEFINED BUILD_GTEST)
+  set (BUILD_GTEST OFF CACHE BOOL "${BUILD_GTEST_DESCR}")
+endif()
+
 # Rebuild *.yacc and *.lex files that are contained by TKMath toolkit
 list (FIND BUILD_TOOLKITS TKMath   CAN_REBUILD_PDC_FOR_TKMATH)
 list (FIND BUILD_TOOLKITS StepFile CAN_REBUILD_PDC_FOR_STEPFILE)
@@ -1184,6 +1194,29 @@ foreach (BUILD_TOOLKIT ${BUILD_TOOLKITS})
   add_subdirectory ("${OCCT_${BUILD_TOOLKIT}_FILES_LOCATION}")
 endforeach()
 
+# Setup Google Test integration if enabled
+if (BUILD_GTEST)
+  OCCT_INCLUDE_CMAKE_FILE ("adm/cmake/gtest")
+  enable_testing()
+
+  OCCT_INCLUDE_CMAKE_FILE ("adm/cmake/occt_gtest")
+  # Initialize GTest environment and create the target first
+  OCCT_INIT_GTEST()
+  
+  # Collect test files from all active toolkits and add them to the target
+  foreach (BUILD_TOOLKIT ${BUILD_TOOLKITS})
+    OCCT_COLLECT_TOOLKIT_TESTS(${BUILD_TOOLKIT})
+  endforeach()
+  
+  # Set environment variables for all tests
+  OCCT_SET_GTEST_ENVIRONMENT()
+else()
+  # Disable GTest integration if not enabled
+  OCCT_CHECK_AND_UNSET_GROUP ("3RDPARTY_GTEST")
+  OCCT_CHECK_AND_UNSET_GROUP ("GTest")
+  OCCT_CHECK_AND_UNSET ("INSTALL_GTEST")
+endif()
+
 if (BUILD_DOC_Overview OR BUILD_DOC_RefMan)
   OCCT_INCLUDE_CMAKE_FILE ("adm/cmake/occt_doc")
   # Setup documentation targets