Deliverance error: no element found in theme
rule: <append theme=".//div[@id='foo']" content=".//div[@id='bar']"/>

Deliverance error: multiple elements found in theme
rule: <append theme=".//div[@class='foo']" content=".//div[@id='bar']"/>
<div class="foo">Dummy Content</div><div class="foo">Dummy Content</div>

Deliverance error: no content matched
rule: <append theme=".//div[@id='foo']" content="//div[@id='bar']"/>