:((( I am still unsure where you missed it out. but it has to be either registerTestlibCmd, registerInteraction, registerValidation, or registerGen in the first line of a main function that needs to use testlib.

In testlib's source code it is like this:

    ~TestlibFinalizeGuard() {
        bool _alive = alive;
        alive = false;

        if (_alive) {
            if (testlibMode == _checker && quitCount == 0)
                __testlib_fail("Checker must end with quit or quitf call.");

            if (testlibMode == _validator && readEofCount == 0 && quitCount == 0)
                __testlib_fail("Validator must end with readEof call.");

            /* opts */
            autoEnsureNoUnusedOpts();

            if (!registered)
                __testlib_fail("Call register-function in the first line of the main (registerTestlibCmd or other similar)");
        }

        if (__testlib_exitCode == 0) {
            validator.writeTestOverviewLog();
            validator.writeTestMarkup();
            validator.writeTestCase();
        }
    }

and the functions that change registered are only the four functions said above. So clearly something has to be missing. I hope you find it well...