$backend = 'XML::SAX::ExpatXS';
my $xml_x_s_exs;
{
    local $ENV{XML_SIMPLE_PREFERRED_PARSER} = $backend;

    $start = time();
    $xml_x_s_exs = $xs->XMLin($XMLFile);
    $end = time();
}

print_result($backend, $end, $start, $size);

...

is_deeply($xml_default, $xml_x_s_exs);