This tests whether inserting elements creates as few copies as I think is possible. If this fails it just means that the container might be a little inefficient.

This test fail because it's using unordered's internal allocator traits, which doesn't work on Visual C++ 7.1. It normally uses the one from Boost.Container by default.

boost::is_nothrow_move_constructible and boost::is_nothrow_move_assignable don't seem to work on this compiler. I'd hope that anyone wanting noexcept support would use a more recent compiler anyway.