Updated the gtest cmake to adopt Ubuntu 20 >= fetchcontent feature, still compatible with ubuntu 18

test/CMakeLists.txt

 # Retrieve googletest from github & compile
 add_subdirectory(gtest)
 
-# Include gtest directory.
-include_directories(${GTEST_INCLUDE_DIRS})
-
 ############# USE THIS TEST AS AN EXAMPLE ####################
 #                                                            #
 # Create a specific test executable for gtest_example        #
 # gnss_utils_add_gtest(gtest_example gtest_example.cpp)      #
-# target_link_libraries(gtest_example ${PROJECT_NAME})       #
 #                                                            #
 ##############################################################
 
 # Navigation test
 gnss_utils_add_gtest(gtest_navigation gtest_navigation.cpp)
-target_link_libraries(gtest_navigation libgtest ${PROJECT_NAME})
 
 # Observations test
 gnss_utils_add_gtest(gtest_observations gtest_observations.cpp)
-target_link_libraries(gtest_observations libgtest ${PROJECT_NAME})
 
 # TDCP test
 gnss_utils_add_gtest(gtest_tdcp gtest_tdcp.cpp)
-target_link_libraries(gtest_tdcp ${PROJECT_NAME})
 
 # Transformations test
 gnss_utils_add_gtest(gtest_transformations gtest_transformations.cpp)
-target_link_libraries(gtest_transformations ${PROJECT_NAME})
 
 # ChiSquare test
-gnss_utils_add_gtest(gtest_chisquare gtest_chisquare.cpp)
-target_link_libraries(gtest_chisquare ${PROJECT_NAME})
\ No newline at end of file
+gnss_utils_add_gtest(gtest_chisquare gtest_chisquare.cpp)
\ No newline at end of file

test/gtest/CMakeLists.txt

-cmake_minimum_required(VERSION 2.8.8)
-project(gtest_builder C CXX)
+if(${CMAKE_VERSION} VERSION_LESS "3.11.0") 
+  message("CMake version less than 3.11.0")
 
-# We need thread support
-#find_package(Threads REQUIRED)
+  # Enable ExternalProject CMake module
+  include(ExternalProject)
 
-# Enable ExternalProject CMake module
-include(ExternalProject)
+  set(GTEST_FORCE_SHARED_CRT ON)
+  set(GTEST_DISABLE_PTHREADS OFF)
 
-set(GTEST_FORCE_SHARED_CRT ON)
-set(GTEST_DISABLE_PTHREADS OFF)
+  # For some reason I need to disable PTHREADS
+  # with g++ (Ubuntu 4.9.3-8ubuntu2~14.04) 4.9.3
+  # This is a known issue for MinGW :
+  # https://github.com/google/shaderc/pull/174
+  #if(MINGW)
+  #    set(GTEST_DISABLE_PTHREADS ON)
+  #endif()
 
-# For some reason I need to disable PTHREADS
-# with g++ (Ubuntu 4.9.3-8ubuntu2~14.04) 4.9.3
-# This is a known issue for MinGW :
-# https://github.com/google/shaderc/pull/174
-#if(MINGW)
-    set(GTEST_DISABLE_PTHREADS ON)
-#endif()
+  # Download GoogleTest
+  ExternalProject_Add(googletest
+      GIT_REPOSITORY https://github.com/google/googletest.git
+      GIT_TAG        v1.8.x
+      # TIMEOUT 1 # We'll try this
+      CMAKE_ARGS -DCMAKE_ARCHIVE_OUTPUT_DIRECTORY_DEBUG:PATH=DebugLibs
+      -DCMAKE_ARCHIVE_OUTPUT_DIRECTORY_RELEASE:PATH=ReleaseLibs
+      -DCMAKE_CXX_FLAGS=${MSVC_COMPILER_DEFS}
+      -Dgtest_force_shared_crt=${GTEST_FORCE_SHARED_CRT}
+      -Dgtest_disable_pthreads=${GTEST_DISABLE_PTHREADS}
+      -DBUILD_GTEST=ON
+      PREFIX "${CMAKE_CURRENT_BINARY_DIR}"
+      # Disable install step
+      INSTALL_COMMAND ""
+      UPDATE_DISCONNECTED 1 # 1: do not update googletest; 0: update googletest via github
+  )
 
-# Download GoogleTest
-ExternalProject_Add(googletest
-    GIT_REPOSITORY https://github.com/google/googletest.git
-    GIT_TAG        v1.8.x
-    # TIMEOUT 1 # We'll try this
-    CMAKE_ARGS -DCMAKE_ARCHIVE_OUTPUT_DIRECTORY_DEBUG:PATH=DebugLibs
-    -DCMAKE_ARCHIVE_OUTPUT_DIRECTORY_RELEASE:PATH=ReleaseLibs
-    -DCMAKE_CXX_FLAGS=${MSVC_COMPILER_DEFS}
-    -Dgtest_force_shared_crt=${GTEST_FORCE_SHARED_CRT}
-    -Dgtest_disable_pthreads=${GTEST_DISABLE_PTHREADS}
-    -DBUILD_GTEST=ON
-    PREFIX "${CMAKE_CURRENT_BINARY_DIR}"
-    # Disable install step
-    INSTALL_COMMAND ""
-    UPDATE_DISCONNECTED 1 # 1: do not update googletest; 0: update googletest via github
-)
+  # Get GTest source and binary directories from CMake project
 
-# Get GTest source and binary directories from CMake project
+  # Specify include dir
+  ExternalProject_Get_Property(googletest source_dir)
+  set(GTEST_INCLUDE_DIRS ${source_dir}/googletest/include PARENT_SCOPE)
 
-# Specify include dir
-ExternalProject_Get_Property(googletest source_dir)
-set(GTEST_INCLUDE_DIRS ${source_dir}/googletest/include PARENT_SCOPE)
+  # Specify MainTest's link libraries
+  ExternalProject_Get_Property(googletest binary_dir)
+  set(GTEST_LIBS_DIR ${binary_dir}/googlemock/gtest PARENT_SCOPE)
 
-# Specify MainTest's link libraries
-ExternalProject_Get_Property(googletest binary_dir)
-set(GTEST_LIBS_DIR ${binary_dir}/googlemock/gtest PARENT_SCOPE)
+  # Create a libgtest target to be used as a dependency by test programs
+  add_library(libgtest IMPORTED STATIC GLOBAL)
+  add_dependencies(libgtest googletest)
 
-# Create a libgtest target to be used as a dependency by test programs
-add_library(libgtest IMPORTED STATIC GLOBAL)
-add_dependencies(libgtest googletest)
+  # Set libgtest properties
+  set_target_properties(libgtest PROPERTIES
+      "IMPORTED_LOCATION" "${binary_dir}/googlemock/gtest/libgtest.a"
+      "IMPORTED_LINK_INTERFACE_LIBRARIES" "${CMAKE_THREAD_LIBS_INIT}"
+  )
 
-# Set libgtest properties
-set_target_properties(libgtest PROPERTIES
-    "IMPORTED_LOCATION" "${binary_dir}/googlemock/gtest/libgtest.a"
-    "IMPORTED_LINK_INTERFACE_LIBRARIES" "${CMAKE_THREAD_LIBS_INIT}"
-)
+else()
 
+  message("CMake version equal or greater than 3.11.0")
+
+  include(FetchContent)
+
+  FetchContent_Declare(
+    googletest
+    GIT_REPOSITORY https://github.com/google/googletest.git 
+    GIT_TAG main)
+
+  FetchContent_MakeAvailable(googletest)
+    
+endif()
+  
 function(gnss_utils_add_gtest target)
   add_executable(${target} ${ARGN})
-  add_dependencies(${target} libgtest)
-  target_link_libraries(${target} libgtest)
-
-  #WORKING_DIRECTORY ${CMAKE_BINARY_DIR}/bin
+  if(${CMAKE_VERSION} VERSION_LESS "3.11.0") 
+    add_dependencies(${target} libgtest)
+    target_link_libraries(${target} libgtest ${PROJECT_NAME})
+    target_include_directories(${target} PUBLIC ${GTEST_INCLUDE_DIRS})
+  else()
+    target_link_libraries(${target} PUBLIC gtest_main ${PROJECT_NAME})
+  endif()
   add_test(NAME ${target} COMMAND ${target})
 endfunction()