Dwsjoquist/add tests for existing sd web service mocks

ASDA tests need something more than the simple mock response queue that SDWebService currently uses, to ensure we don't break existing functionality when we modify that, here is the plan:
1. create set of async unit tests to fully test the mock queue response methods in SDWebService
2. extract the mock queue response methods into their own class, replacing the direct implementation in SDWebService with a protocol based approach
3. add the new mock response class that ASDA tests need (mapping based, not queue based)

This PR implements step 1