The test cases inside tmxmlWriter are being executed using the class
net.ontopia.topicmaps.utils.ltm.test.LTMTopicMapWriterTestGenerator.class.
This test suite is a bit complex, so here is a brief explanation of what each directory is for:

in        Contains normal input files.
tmxml     TMXML export directory for 'in'.
          Ids should be preserved for all files in 'in'.
out       Canonicalization directory of files in 'tmxml'.
baseline  Canonicalization directory of files in 'in'.

filter-in        Contains normal input files.
filter-ltm       TMXML export directory for 'in'.
                 Ids should be preserved for all files in 'in'.
filter-out       Canonicalization directory of files in 'tmxml'.
filter-baseline  Canonicalization directory of files in 'in'.

x-in        Like 'in', but for special cases.
x-tmxml     TMXML export directory for 'x-in'
x-out       Canonicalization of files in 'x-tmxml'
x-baseline  Like baseline, but cannot be created automatically from source
            (needs manual intervention).

NOTE: in, filter-in and x-in may contain the sub-folders 'error' and 'failure'.
These directories are for files that cause error or failure, but shouldn't,
or for which we should find out why the error/failure occurrs.
            
NOTE: The directories 'tmxml', 'out', 'filter-tmxml', 'filter-out', 'x-tmxml'
and 'x-out' are all autogenerated, and so are not checked into CVS.