How to use CMake with Catch2?

From Catch2's example, I tried to run this example with cmake where structure of my project is like this:

/factorial
    +-- CMakeLists.txt
    +-- /bin
    +-- /include
    |     +-- catch.hpp
    |     +-- fact.hpp 
    +-- /src
    |     +-- CMakeLists.txt
    |    +-- fact.cpp
    +-- /test
         +-- CMakeLists.txt
         +-- test_fact.cpp

fact.cpp:

unsigned int factorial( unsigned int number ) {
    return number <= 1 ? number : factorial(number-1)*number;
}

fact.hpp:

#ifndef FACT_H
#define FACT_H

unsigned int factorial(unsigned int);

#endif

test_fact.cpp:

#define CATCH_CONFIG_MAIN
#include "catch.hpp"
#include "fact.hpp"

TEST_CASE( "factorials are computed", "[factorial]" ) {
    REQUIRE( factorial(1) == 1 );
    REQUIRE( factorial(2) == 2 );
    REQUIRE( factorial(3) == 6 );
    REQUIRE( factorial(10) == 3628800 );
}

I tried several ways already to build this project with cmake but it's failed. Sometimes I got an error:

cpp:X:XX: fatal error: 'fact.hpp' file not found
...

and sometimes I got:

Undefined symbols for architecture x86_64:
  "_main", referenced from:
...

when I run make.

What should I have in factorial/CMakeLists.txt,factorial/src/CMakeLists.txt and factorial/test/CMakeLists.txt, if I want to have my execution files in factorial/bin?

Additional: This is my CMakeLists.txts (I think they are completely wrong).

factorial/CMakeLists.txt:

project(factorial)
cmake_minimum_required(VERSION 2.8.12)

add_definitions("-std=c++11")
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_SOURCE_DIR}/bin)

add_subdirectory(src)
add_subdirectory(test)

factorial/src/CMakeLists.txt:

project(factorial)
cmake_minimum_required(VERSION 2.8.12)

add_executable(fact fact.cpp)

factorial/test/CMakeLists.txt:

project(factorial)
cmake_minimum_required(VERSION 2.8.12)

add_executable(test_fact test_fact.cpp)
target_include_directories(test_fact PRIVATE ${CMAKE_SOURCE_DIR}/include)

Solution

Many problems here:

add_executable(fact fact.cpp)

The call should be using add_library (You could also specify STATIC or SHARED), since you are only defining a factorial function, not an executable with a main function.

add_executable(fact fact.cpp)

The file should be test_fact.cpp and the target should have a different name to avoid conflict with the previous library you created. Also, your fact.cpp doesn't include fact.hpp. Last but not least, instead of doing target_include_directories, just write the following in your top-level CMakeLists.txt:

include_directories(include)

Now, all subdirectories should be able to access the header files. Beware that this removes control of the scoping of the header files (PRIVATE vs PUBLIC vs INTERFACE) and allows all subdirectories to access the header files. If you want to restrict this behavior, then use target_include_direcories for all targets (Your library and the test executable). For this example, since everything needs to access the header files, there is no problem with the statement above.