Surrogate Code Points in Tests?

In looking at test:

   prefix_with_PN_CHARS_BASE_character_boundaries.ttl  [1]

There are the code points u+dc00, u+db7f, and u+dfff in the last part of
the prefix.  The code points u+d800-u+dfff are not valid unicode characters.

Why are these in a positive test?

[1]
https://dvcs.w3.org/hg/rdf/raw-file/default/rdf-turtle/tests-ttl/prefix_with_PN_CHARS_BASE_character_boundaries.ttl

-- 
--Alex Milowski
"The excellence of grammar as a guide is proportional to the paucity of the
inflexions, i.e. to the degree of analysis effected by the language
considered."

Bertrand Russell in a footnote of Principles of Mathematics