CLion is my preferred C++ IDE. For my Master’s thesis, today I had to implement the calculation of Shapley’s value - a concept from game theory.
I thought, okay, let’s do this properly. I’ll be using the calculation inside a simulator, but I want to implement it outside the scope of this huge code framework, so that I can run easily unit-test it. So I’ll use CLion and let it compile a library. Later in the simulator I can just link the library in. My unit testing binary also just links the library. So if later I fix some bugs or add some functionality, I can easily run my tests to see if I broke anything, and then let it run on my simulator, without the hassle of copying over the code.

CLion uses CMake to compile things. CMake is a wrapper for Makefiles. It has its own language and generates the Makefiles for you - it’s a bit like SASS for CSS.
Let’s see how to set up this whole thing in CLion.

Create a new project which I’ll call shapley. src/shapley.{cpp,h} will describe the library functionality. src/tests/unittests.cpp will describe a binary that runs the unit tests. So the initial folder structure is this:

src/
  lib/
    CMakeLists.txt
    shapley.cpp
    shapley.h    
  tests/
    CMakeLists.txt
    unittests.cpp  
CMakeLists.txt

Note the three CMakeList.txt’s. The one inside src/tests/ is for compiling just the unit tests. src/lib/CMakeLists.txt handles the library compilation. The top one includes both others and handles global configuration rules.

First the src/tests/CMakeLists.txt:

cmake_minimum_required(VERSION 3.8)
set(CMAKE_CXX_STANDARD 11)
project(shapley-unittests)

include_directories(..)

find_library(LIBRARY-PATH :libcppunit.so)
link_directories(${LIBRARY-PATH})

set(SOURCE_FILES_UNITTESTS
        unittests.cpp
)

set(CMAKE_BUILD_TYPE Debug)
add_executable(unittests ${SOURCE_FILES_UNITTESTS})
target_link_libraries(unittests shapley :libcppunit.so)

include_directories(..) includes the src/ directory so that we can include the library header as #include "shapley.h".
set(SOURCE_FILES_UNITTESTS ...) sets this project’s source files. Note that this is only the unittests.cpp.
target_link_libraries(unittests shapley :libcppunit.so) links both the libshapley.a and the libcppunit.so.

Secondly src/lib/CMakeLists.txt:

cmake_minimum_required(VERSION 3.8)
set(CMAKE_CXX_STANDARD 11)
project(shapley-lib)

include_directories(..)

set(SOURCE_FILES_SHAPLEY-LIB
        shapley.cpp
        shapley.h)

add_library(shapley ${SOURCE_FILES_SHAPLEY-LIB})

Finally the top CMakeLists.txt:

cmake_minimum_required(VERSION 3.8)
project(shapley)

set(CMAKE_CXX_STANDARD 11)

add_subdirectory(src/tests)
add_subdirectory(src/lib)

set_target_properties(unittests PROPERTIES RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/out/")
set_target_properties(shapley PROPERTIES ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/out/")

add_subdirectory() includes the other CMakeLists.txts.
The set_target_properties simply set the output directory.

This covers the CMake setup. Now your src/tests/unittests.cpp can simply do this:

#include <iostream>
#include "shapley.h"

int main(int argc, const char *argv[]) {
	hello();
	std::cout << "Hello World" << std::endl;
	return 0;
}

and define hello() in your library, and it’ll work.