The test checks the special var $sys a.k.a $opt a.k.a $system

>>>>templates/test.tpl
{$opt.const.SAMPLE_CONST}
{$sys.const.SAMPLE_CONST}
{$system.const.SAMPLE_CONST}

>>>>data.php
define('SAMPLE_CONST', 'foo');

>>>>expected.txt
OUTPUT

>>>>result.txt
foo
foo
foo