The test checks if opt:single cannot be applied to the OPT tags.

>>>>templates/test.tpl
<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
<opt:root>
<foo>
<opt:bar opt:single="yes">
This will not be visible.
</opt:bar>
</foo>
</opt:root>

>>>>expected.txt
Opt_AttributeInvalidNamespace_Exception