Someone already wrote this for you - there is a "hello world" in the Boost docs .
In your case, I think it should look something like this:
#include "A.hpp"
#define BOOST_TEST_MODULE MyTest
#include <boost/test/unit_test.hpp>
BOOST_AUTO_TEST_CASE( my_test )
{
my_class A( );
BOOST_CHECK( A.multiply_by_two(2) == 4 );
}
EDIT:
, , .