Use mock MongoDB server for unit test

I don’t know about Python, but I had a similar concern with C#. I decided to just run a real instance of Mongo on my workstation pointed at an empty directory. It’s not great because the code isn’t isolated but it’s fast and easy.

Only the data access layer actually calls Mongo during the test. The rest can rely on the mocks of the data access layer. I didn’t feel like faking Mongo was worth the effort when really I want to verify the interaction with Mongo is correct anyway.

You could try: https://github.com/vmalloc/mongomock, which aims to be a small library for mocking pymongo collection objects for testing purposes.

However, I'm not sure that the cost of just running mongodb would be prohibitive compared to ensuring some mocking library is feature complete.