The pipeline
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc" xmlns:test="http://test" version="3.0">
<p:output port="result"/>
<p:declare-step type="test:test">
<p:input port="source"/>
<p:output port="result"/>
<p:identity/>
</p:declare-step>
<p:identity>
<p:with-input>
<doc>
<value>5</value>
</doc>
</p:with-input>
</p:identity>
<test:test>
<p:with-input>
<result>{/doc/value/text()}</result>
</p:with-input>
</test:test>
</p:declare-step>
Schematron validation
<s:schema xmlns="http://www.w3.org/1999/xhtml" xmlns:s="http://purl.oclc.org/dsdl/schematron" queryBinding="xslt2">
<s:pattern>
<s:rule context="/">
<s:assert test="/result">Document root is not named 'result'.</s:assert>
<s:assert test="count(*) = 1">Document does not have exactly one child element.</s:assert>
<s:assert test="/result/text()='5'">Element 'result' does not have a text child with '5'.</s:assert>
</s:rule>
</s:pattern>
</s:schema>
