Add a new test subdirectory

How to integrate a new test directory in the build

1. create the new test subdirectory in the module $m (eg. m='channels/smartcard/client'):

mkdir $m/test

2. create the test source;
3. create a $m/test/CMakeLists.txt file (take one from another test subdirectory as example).
4. edit the target_link_libraries to add the library of the module you want to test. (eg. if the module to test is smartcard-client, add that):

target_link_libraries(${MODULE_NAME} ${${MODULE_PREFIX}_LIBS} smartcard-client)

5. edit the $m/CMakeLists.txt file in the parent directory, adding the test subdirectory to the buid:

if(BUILD_TESTING)
	add_subdirectory(test)
endif()
```

That's it: Compile and run the tests!