Tests p:unwrap to change content-type to "text/plain" for empty document node.
Test ab-unwrap-013.xml is expected to pass.
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc" name="pipeline" version="3.0">
<p:output port="result"/>
<p:unwrap match="root">
<p:with-input>
<p:inline document-properties="map{'base-uri' : 'http://xproc.org/ns/testsuite/3.0', 'serialization' : map{'indent' : true()}}">
<root/>
</p:inline>
</p:with-input>
</p:unwrap>
<p:identity>
<p:with-input>
<result>{p:document-property(., 'content-type')}</result>
</p:with-input>
</p:identity>
</p:declare-step>
<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">The root element is not 'result'.</s:assert>
<s:assert test="result/text()='text/plain'">The content-type is not text/plain.</s:assert>
</s:rule>
</s:pattern>
</s:schema>
New test.