The test uses the following expression:

(resolve-uri('prod', 'http://datypic.com/'), resolve-uri('prod2', 'http://datypic.com/prod1'), resolve-uri( 'http://example.org','http://datypic.com'), resolve-uri( 'http://datypic.com', '../base'), resolve-uri( '', 'http://datypic.com'))

The following subexpression does not have a valid $base URI: 

resolve-uri( 'http://datypic.com', '../base')

The spec says, on FORG0002:

"A dynamic error is raised [err:FORG0002] if $base is not a valid IRI according to the rules of RFC3987, extended with an implementation-defined subset of the extensions permitted in LEIRI, or if it is not a suitable IRI to use as input to the chosen resolution algorithm (for example, if it is a relative IRI reference, if it is a non-hierarchic URI, or if it contains a fragment identifier)."

I.e., the last part "i.e.... if it is a relative IRI reference".


This test exists for a while already, perhaps this has changed since XPath 2.0?