I have moved the files to that directory and checked them in.

I'm still not seeing these files.

errors-and-optimization-1.txt has been checked in, but errors-and-optimization-3.txt still seems to be missing

I now see errors-and-optimization-3.txt, which contains "false", but this is not the correct result for the query:

let $N :=  <n x="this ain't no date"/>
return $N[if (@x castable as xs:date)
   then xs:date(@x) gt xs:date("2000-01-01")
   else false()]

I changed the results file to an empty file (is that the right way to represent an empty sequence in the results?)

If the expected result is an empty sequence, it's generally clearer to wrap a call of count() around it and publish an expected result of "0".

I see that you've followed Mike's suggestion in Comment #6.

I've removed the trailing CR from your result file.

This test case now passes for me.