Document base struct.(init, collection_name, , ,)
use pymongo (not use mongomock) on EngineTest
create collection wrapper.
use 2to3
remove unused mongomock.
remove unused mongomock.
divide testcae.
python 2.x and 3.x
cleanup test.
stand-by py.test
recovery test_document.
remove old Document, Collection
recovery test_document.
refactor for PEP8, pylint
remove submodules/mongomock