The purpose of mocking is to skip the complexity and unit test own code. If you want to write e2e tests then use the db.
Writing code to setup/teardown a testing DB for unit testing is technical debt and incredibly unsatisfying.
There are mock libraries in npm:
mongo - https://www.npmjs.com/package/mongomock
mongoose - https://www.npmjs.com/package/mockgoose
If those don't support the features you need, then yes you may need to use the real thing.
