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Said test's expected results are all the ASCII characters 1-31 escaped. However, ASCII 9 (tab) and 10 (newline) don't need to be escaped since they are perfectly valid in XML.
The catalog entry for the test says compare="Fragment", and the rules for compare="Fragment" are such that the supplied "expected output" of this test will compare equal to the actual output of a conformant processor. So the supplied test results are not technically incorrect. The test framework wasn't really designed to enable serializers to be tested. At one point I think "compare='Text'" was intended for this purpose, but somewhere along the line its meaning was changed to be the same as compare="Fragment".
Dear Paul, following the comment of Mike, my suggestion would be to leave as is.