I have used a similar technique to subvert Perl builtins and mimic system errors:

use Errno qw( ENOSPC );
{
    local *CORE::GLOBAL::print = sub { $! = ENOSPC; return};
    # make test call
    # see what happens when a device is full
}
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A finer grained and more accurate test can be obtained by localizing an open file handle:

{
    open local(LOG), '>>', '/dev/full' or die $!;
    # /dev/full is a Linux thing
    # call the test
}
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++adrianh for bringing this up, there is a wealth of devious fun in this idiom.

After Compline,
Zaxo