The pipeline
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
<p:output port="result"/>
<p:xslt version="3.0" template-name="start">
<p:with-input>
<p:empty/>
</p:with-input>
<p:with-input port="stylesheet">
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="3.0">
<xsl:template name="start">
<xsl:result-document href="something"/>
</xsl:template>
</xsl:stylesheet>
</p:with-input>
</p:xslt>
<p:identity>
<p:with-input pipe="secondary"/>
</p:identity>
<p:identity>
<p:with-input>
<result>
<content-type>{p:document-property(., 'content-type')}</content-type>
<children>{count(//node())}</children>
</result>
</p:with-input>
</p:identity>
</p:declare-step>
Schematron validation
<s:schema xmlns:s="http://purl.oclc.org/dsdl/schematron" queryBinding="xslt2">
<s:pattern>
<s:rule context="/">
<s:assert test="result">The root element is not 'result'.</s:assert>
<s:assert test="result/content-type/text()='application/xml'">The result's content-type is not "application/xml".</s:assert>
<s:assert test="result/children/text()='0'">The result's number of children is not 0.</s:assert>
</s:rule>
</s:pattern>
</s:schema>
