memfs
In-memory file-system with Node's fs API.
node-schedule
A cron-like and not-cron-like job scheduler for Node.
ioredis-mock
This library emulates ioredis by performing all operations in-memory.
lokijs
Fast document oriented javascript in-memory database
fake-indexeddb
Fake IndexedDB: a pure JS in-memory implementation of the IndexedDB API