Hi Patrick,
To test your development you can either use the new DataSHIELD Interface (see the discusssion here: Datashield R API) or the “traditional” way by uploading the function as a script in your server (you can find a lot of information in the DataSHIELD wiki: https://data2knowledge.atlassian.net/wiki/spaces/DSDEV/pages/12943448/Notes+for+developers). Otherwise, we can arrange a skype call where I can show you how you can test the function.