Ken,
One thing I would double-check is the actual value in the Message Type field (MSH:9) compared to the message type HL7 layout you are using in the xlate. If you are doing a PATHCOPY, or copying the input value in MSH:9 to the output record, the testing tool is going to validate against the record layout based on the value in MSH:9; i.e. if MDM^T02 is being copied to MSH:9 in the outbound record, then I think the tester is going to validate against the MDM_T02 outbound layout in your variant, rather than the ORU layout that is defined in your xlate.
Hope this helps.
Jim Cobane
Henry Ford Health