In catalog-schema.xsd, for “assert-serialization-error” it says:

Asserts that the query can be executed without error, but serializing the result produces a serialization error. The expression result is serialized using the default serialization parameters method="xml" indent="no" omit-xml-declaration="yes”.

But there are a number of tests in OptionDecl.serialization.xml that seem to expect different serialization parameters.  For example, Serialization-032:

   <test-case name="Serialization-032">
      ...
      <test><![CDATA[
         declare namespace output = "http://www.w3.org/2010/xslt-xquery-serialization";
         declare option output:method "xml";
         declare option output:standalone "no";
         declare option output:omit-xml-declaration "yes";
		 <a/>
      ]]></test>
      <result>
        <assert-serialization-error code="SEPM0009" />
      </result>
   </test-case>

This test seems to expect that the serialization parameters from the prolog of the query will be used. (SEPM009 results if the omit-xml-declaration parameter has the value yes, and the standalone parameter has a value other than omit)

It appears that either the definition of assert-serialization-error is wrong or the tests are wrong.