mongomock is a package to do just what the name implies, mocking a mongo database.
To use with mongoengine, simply specify mongomock when connecting with mongoengine:
connect('mongoenginetest', host='mongomock://localhost')
conn = get_connection()or with an alias:
connect('mongoenginetest', host='mongomock://localhost', alias='testdb')
conn = get_connection('testdb')