maint-5-2/tapestry-core/src/test/resources/org/apache/tapestry5/internal/services/extend_must_be_root.tml

<t:content xmlns:t="http://tapestry.apache.org/schema/tapestry_5_1_0.xsd">
    <p>
        <t:extend>Not allowed to be nested!</t:extend>
    </p>
</t:content>