Do it exist some problems with 1.8.0 ? I've just switched to rb_define_alloc_func() and with testunit-0.1.5 the results are pigeon% ruby -v ruby 1.6.8 (2002-12-24) [i686-linux] pigeon% pigeon% make test ruby tests/writer.rb Loaded suite tests/writer Started .......... Finished in 0.531359 seconds. 9 tests, 292 assertions, 0 failures, 0 errors ruby tests/reader.rb Loaded suite tests/reader Started .................. Finished in 0.380022 seconds. 17 tests, 792 assertions, 0 failures, 0 errors pigeon% pigeon% ruby -v ruby 1.8.0 (2002-12-24) [i686-linux] pigeon% pigeon% make test ruby tests/writer.rb Loaded suite tests/writer Started .......... Finished in 0.943341 seconds. 9 tests, 292 assertions, 0 failures, 0 errors ruby tests/reader.rb Loaded suite tests/reader Started .................. Finished in 0.728915 seconds. 17 tests, 792 assertions, 0 failures, 0 errors pigeon% Guy Decoux