Self-Testing Code Block

Self-Testing Code Block

Sometimes an assertion, unit test, or debug tracing printout is too small to check everything. Then you have to write a bigger chunk of self-testing code. The traditional way to do this in code is to wrap it in a preprocessor macro:

    #if YDEBUG
       ... // block of test code
    #endif

Another reason to use a different type of self-testing code than assertions is that you've probably decided to leave the simpler assertions in production code. A simple test like this is probably fine for production:

    yassert(ptr != NULL);  // Fast

But a bigger amount of arithmetic may be something that's not for production:

    yassert(aussie_vector_sum(v, n) == 0.0);  // Slow

So, you probably want to have macros and preprocessor settings for both production and debug-only assertions and self-testing code blocks. The simple way looks like this:

    #if YDEBUG
    yassert(aussie_vector_sum(v, n) == 0.0);
    #endif

Or you could have your own debug-only version of assertions that are skipped for production mode:

    yassert_debug(aussie_vector_sum(v, n) == 0.0);

The definition of “yassert_debug” then looks like this in the header file:

    #if YDEBUG
    #define yassert_debug(cond) yassert(cond)  // Debug mode
    #else 
    #define yassert_debug(cond)  // nothing in production
    #endif

This makes the “yassert_debug” macro a normal assertion in debug mode, but the whole coded expression disappears to nothing in production build mode. The above example assumes a separate set of build flags for a production build.

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