Created a XML to USPS round-trip test that passes. This just tests their end point, to is still labeled '_todo.' Created a non-passing test for a 200 to be returned from a user json request to our service. Test constants in the file 'usps_test_data'
Cleaned up usps_test_data file a bit. User JSON is now accepted with a 200. Will set up broken test to check proper parsing of user data next.
Stubbing out the models file, with a stub method to convert the user request json to xml for a usps request.
Finished XMLRequestGenerator in 'models,' which could have been named something else, oh well. Tests pass. Next, I'll change the test to use the xml generated from the user submitted JSON to make the USPS request.
One test now tracks the conversion of user JSON to a XML and the request to USPS. Next, will break the test to expect the returned XML to match  a JSON response after conversion by the stubbed out method 'convert_xml_to_dict' in the renamed USPSService class, models.py. Sleep now.
Failing test in place for complete round trip, user json -> service xml -> usps response xml -> service response json -> user. Route logic in place, just need to finish the stubbed out usps xml -> service response json method.
Full round trip works, test passes. If the request is out of bound for some field, like weight, I'm just returning the error description to the user for now. I would write a method to log and handle the error and return a cusome error message to the user.
Forgot a debug print...