Test p:viewport raises XS0107 for statically invalid match value.
Test ab-viewport-025.xml is expected to fail with error code err:XS0107.
<p:declare-step xmlns:err="http://www.w3.org/ns/xproc-error" xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
   <p:output port="result">
   <p:viewport match="i-do-not-exist()">
      <p:with-input>
         <doc/>
      </p:with-input>
      <p:add-attribute match="/*" attribute-name="att" attribute-value="3">
   </p:viewport>
</p:declare-step>
Additional tests for p:viewport (partly ported from 1.0)