The mappings can be tested using an online harvester. It will harvest a certain repository and uses the mapping to provide a result which is directly shown on screen. This may help in testing the mapping.
The mapping can be tested in two ways.
First by giving it a url which provides a OAI ListRecords answer. Something like: http://repository.example.org/oai?verb=ListRecords&metadataPrefix=oai_dc
Secondly you can use one of the repositories known by Meresco Harvester.