Its a dynamic error, if @content-type is not valid..
Test ab-http-request-116.xml is expected to fail with error code err:XD0079 [XProc, Core steps].
<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:http-request href="http://localhost:8246/service/fixed-xml" parameters="map{'override-content-type' : 'surely-not-correct'}">
      <p:with-input>
         <p:empty/>
      </p:with-input>
   </p:http-request>
</p:declare-step>
Changed the value of the href option to an HTTP URI.
               The value isn’t relevant to the test, but processors are allowed to reject
               schemes other than http(s):.
Additional tests for p:http-request.