BOOST_TEST_MESSAGE(message) unconditionally writes the message into the test runner log file. Unlike BOOST_TEST_CHECKPOINT no file and line number information is written into the log file. The message is applied to an output stream with operator<< and can include other invocations of operator<<.

BOOST_AUTO_TEST_CASE(example_test_message)
{
    int const i = 0;
    BOOST_TEST_MESSAGE("i = " << i);

    BOOST_REQUIRE(i == 0);
}