I would split this up into 3 tests. 

1. One where you use the `FORCE_SEARCH_IMPL` setting and assure that `/_force_api_impl/<setting>` is in the called URL
2. One where you use `self.client.get(url, {'_force_api_impl': 'msaccess'})`  and assure that `/_force_api_impl/msaccess` is in the called URL
3. One where `FORCE_SEARCH_IMPL='hbase'` and use `self.client.get(url, {'_force_api_impl': 'msaccess'})`  and assure that `/_force_api_impl/msaccess` is in the called URL