i believe, it’s pretty cumbersome to test a more complex IDOC with this testcase. You must put many values on the correct position in the base type elements of the inSAPTables parameter.
If you have an IDOC file in his raw format (like SAP creates it for instance with trx WE19), then you could try to read this file and test the IDOC parser. See at http://docu.e2ebridge.com/Reading+IDocs+From+File# how this can be achieved. Once you have the IDOC data in a object of type Tables , you can parse it to your MBGMCR02 class.