Better way:

    /**
    testCode(); testCode();
    /**/

(...)

    /**/
    productionCode(); productionCode();
    /**/

I think this is better because it's much easier to see what you're supposed to do in order to switch the block on or off, and it's only a single character change per block. (though you can't switch from test to production in one character, but meh).

However, I tend to see commented code as ugly cruft. To me, comments are for explaining in natural language what you're doing, not for deactivating bits of code. If it's bad get rid of it, if it's good keep it. Why comment code?

The only time I comment out code is to warn developers away from doing something which is obvious but a bad idea, for example:

    /*
    // This was a neat idea but it makes it break if the user isn't logged in
    userPreference = getPrefFromUserSession();
    */