feature(testing-automation): unit tests with Google Framework (#3273)

src/cmake/googletest.cmake

@@ -0,0 +1,32 @@
+# the following code to fetch googletest
+# is inspired by and adapted after https://crascit.com/2015/07/25/cmake-gtest/
+# download and unpack googletest at configure time
+
+macro(fetch_googletest _download_module_path _download_root)
+    set(GOOGLETEST_DOWNLOAD_ROOT ${_download_root})
+    configure_file(
+            ${_download_module_path}/googletest-download.cmake
+            ${_download_root}/CMakeLists.txt
+            @ONLY
+    )
+    unset(GOOGLETEST_DOWNLOAD_ROOT)
+
+    execute_process(
+            COMMAND
+            "${CMAKE_COMMAND}" -G "${CMAKE_GENERATOR}" .
+            WORKING_DIRECTORY
+            ${_download_root}
+    )
+    execute_process(
+            COMMAND
+            "${CMAKE_COMMAND}" --build .
+            WORKING_DIRECTORY
+            ${_download_root}
+    )
+
+    # adds the targers: gtest, gtest_main, gmock, gmock_main
+    add_subdirectory(
+            ${_download_root}/googletest-src
+            ${_download_root}/googletest-build
+    )
+endmacro()