Do you only need to build the googletest library once? - c++

Question

So firstly I'm new to testing frameworks and relatively new to C++ but am trying to wrap my head around GoogleTest. I'm working on a Windows machine, running "Git for Windows" (MSYS) and MinGW whilst using Sublime Text as my code editor. I am using make as my build tool, although the more I learn about cmake and its cross-platform focus makes me wonder if I should switch to let cmake create makefiles for me. (that's probably a whole other question)
What I'm struggling to understand is what precisly to do with the GoogleTest source package. I realise that I need to build the source into the library and then include that when compiling my tests, but how should I go about doing this? Google includes a cmake build script that generates env/compilier specific makefiles for building. Should I be using this? I feel like if i do so and it blindly works a lot of what is happening under the hood will go over my head. The readme file isn't eliviating my issues, as it implies that i should be building the library and my tests each time i wish the run them. Shouldn't a library be a standalone archive that needs compiling only once? I'm confused and I'm sure its my fault but i'd appreciate it if someone shed some light on this process for me.

Answer 1

You should keep in mind that make will not rebuild gtest if you don't change anything in gtest source code.
Below is my approach to the usage of cmake and gtest for unit testing.
You can add gtest source code by adding it as subdirectory in the root CMakeLists.txt file.
add_subdirectory(${CMAKE_SOURCE_DIR}/thirdparty/gtest ${CMAKE_CURRENT_BINARY_DIR}/gtest)
include_directories(${CMAKE_SOURCE_DIR}/thirdparty/gtest/include ${CMAKE_SOURCE_DIR}/thirdparty/gtest)
My application consist of individual modules containing test folder for unit testing. I have the following boilerplate loop to add each test to the global scope.
file(GLOB TEST_SRC_FILES *.cpp)
foreach(TEST_SRC_PATH ${TEST_SRC_FILES})
#get filename of your test without extension
get_filename_component(TEST_NAME ${TEST_SRC_PATH} NAME_WE)
add_executable(${TEST_NAME} ${TEST_NAME})
#here you link the test executable with gtest
target_link_libraries(${TEST_NAME} gtest gtest_main)
#-----------------------------
# you can link here your test to external libraries
#-----------------------------
add_test(${TEST_NAME} ${TEST_NAME})
#this is a list of all tests
set(PROJECT_TEST_NAMES ${PROJECT_TEST_NAMES} ${TEST_NAME})
endforeach()
#This assigns the list of tests to a property. This make the list available from the root scope.
get_property(UNIT_TESTS GLOBAL PROPERTY UNIT_TESTS)
set(UNIT_TESTS ${UNIT_TESTS} ${PROJECT_TEST_NAMES})
set_property(GLOBAL PROPERTY UNIT_TESTS ${UNIT_TESTS} )
Finally, in the root scope, I add a custom target named check which runs ctest on my unit tests.
#-----------------------------
# Running unit tests
#-----------------------------
get_property(UNIT_TESTS GLOBAL PROPERTY UNIT_TESTS)
if(DEFINED UNIT_TESTS)
add_custom_target(check COMMAND ctest -VV
DEPENDS ${UNIT_TESTS})
endif()
When I run make check, it runs unit tests from all modules, whereas make compiles without tests.