Test err:XS0001 009

The pipeline

<p:declare-step xmlns:err="http://www.w3.org/ns/xproc-error" xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
   <p:choose name="step">
      <p:with-input>
         <p:pipe step="following" port="result"/>
      </p:with-input>
      <p:when test="1 = 1">
         <p:identity>
            <p:with-input port="source">
               <p:inline>
                  <doc/>
               </p:inline>
            </p:with-input>
         </p:identity>
      </p:when>
   </p:choose>
   <p:identity name="following"/>
</p:declare-step>