Tests replacing attribute value with p:add-attribute (attribute name in no namespace).
Test ab-add-attribute-012.xml is expected to pass.
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
   <p:output port="result">
   <p:add-attribute match="/doc" attribute-value="5">
      <p:with-input>
         <doc att="4">
      </p:with-input>
      <p:with-option name="attribute-name" select="'att'">
   </p:add-attribute>
</p:declare-step>
<s:schema xmlns:s="http://purl.oclc.org/dsdl/schematron" queryBinding="xslt2">
   <s:pattern>
      <s:rule context="/">
         <s:assert test="doc">The document root is not doc.</s:assert>
         <s:assert test="doc/@att">There is not attribute "att" at doc.</s:assert>
         <s:assert test="doc/@att=5">Value of attribute "att" is not 5.</s:assert>
      </s:rule>
   </s:pattern>
</s:schema>
Added attribute 'queryBinding' to schematron's schema.
Added new tests for p:add-attribute.