The test checks the basic opt:content functionality.

>>>>templates/test.tpl
<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
<opt:root>
<p opt:content="$foo">Default content</p>
<p opt:content="$bar">Default content</p>
</opt:root>

>>>>expected.txt
OUTPUT

>>>>data.php
$view->bar = 'Modified content';

>>>>result.txt
<p>Default content</p>
<p>Modified content</p>