Mongomock with persistence

This is a package based on the mongomock package to test any code using MongoDB via the PyMongo API.

With mongomock the documents are stored in memory and not available after the process performing the tests exits. In some test cases it is necessary to have a non-volatile (persistent) storage of the database. For example, tests of command line interfaces (CLI) add things into the database and assume they are then available across several processes.

How it works

This package adds an option to store the database in a file. This is accomplished by small extensions of the classes in store.py. These extensions are not intended to keep the database synchronized instantly on disk. Rather the database is eventually dumped to a file only just before the ServerStore object is destroyed. After that the file can be used to create other ServerStore objects in the final state of the original ServerStore object.

When to use

1. In test cases where a database must be used by several consecutive processes and the database state has to be preserved in the meantimes.

2. In tutorials to learn the basics of using PyMongo-based software.

3. In further single-client applications of MongoDB.

In all use cases one has to make sure that all PyMongo features used are covered by mongomock. See this for further details.

How to install

The package can be easily installed using pip:

pip install mongomock-persistence

How to use

To use the package the MongoClient class from this package must be imported instead of that from mongomock. Then the persistence can be activated in two ways:

1. Set the environment variable MONGOMOCK_SERVERSTORE_FILE to the name of a non-empty JSON file (initialized with '{}') and call MongoClient class as usual:

export MONGOMOCK_SERVERSTORE_FILE=/full/path/to/mongomock_file.json

from mongomock_persistence import MongoClient
mongo_client = MongoClient()

2. Create a custom ServerStore object explicitly by using the filename keyword argument and then pass it to MongoClient call:

from mongomock_persistence import MongoClient
mongo_store = ServerStore(filename='/full/path/to/mongomock_file.json')
mongo_client = MongoClient(_store=mongo_store)

How to test

Install the test extra and then run pytest, i.e.

pip install mongomock-persistence[test]
pytest