Re: [boost] Is there interest in unit testing both passing and failing BOOST_MPL_ASSERTs?

Subject: Re: [boost] Is there interest in unit testing both passing and failing BOOST_MPL_ASSERTs?
From: Gordon Woodhull (gordon_at_[hidden])
Date: 2011-09-15 04:24:52

On Sep 15, 2011, at 3:54 AM, Ben Robinson wrote:

> Thank you for your insight into some additional benefits of this
> capability.  

Thank you for making my library properly testable!

> I had not considered the convenience of debugging an actual
> run-time call stack vs. the compiler trace.  I will design this library so
> that by setting a single breakpoint in the library, it will always give
> access to the call-stack leading up to the failed assertion.

Oo.  Neat.  Actually I was just imagining an integrated pretty-print facility like Abel was suggesting, that puts the failed type calculation into the exception string.  

For example, one of my typical tests 

BOOST_MPL_ASSERT(( mpl::equal<preorder_adj::type, mpl::vector<A,B,C,D,E,F,G,A> > ));

currently fails with

depth_first_search.cpp:85:1: error: No match for 'assertion_failed(
        mpl_::failed ************ boost::mpl::equal<
            boost::mpl::v_item<G, boost::mpl::v_item<F, boost::mpl::v_item<E, boost::mpl::v_item<D, boost::mpl::v_item<C, boost::mpl::v_item<B, boost::mpl::v_item<A, boost::mpl::vector<mpl_::na>, 0>, 0>, 0>, 0>, 0>, 0>, 0>
          , boost::mpl::vector<A, B, C, D, E, F, G, A> 
        >::************
    )'

and instead it could throw an exception that includes the gold inside the ***s.

Then when running the unit test in verbose mode, I could verify that the failures are failing for the right reasons.  I don't know much Boost.Test (nor have I looked closely at metatest) but it may even be possible to verify this automatically.

Cheers,
Gordon