use Errno qw( ENOSPC );
{
    local *CORE::GLOBAL::print = sub { $! = ENOSPC; return};
    # make test call
    # see what happens when a device is full
}

##</code><code>##

{
    open local(LOG), '>>', '/dev/full' or die $!;
    # /dev/full is a Linux thing
    # call the test
}