Birdisle (an anagram of "lib redis") is a modified version of redis that runs as a library inside another process. The primary aim is to simplify unit testing by providing a way to run tests against what appears to be a redis server, but without the hassle of starting a separate process and ensuring that it is torn down correctly.
Birdisle-py is Python bindings for Birdisle. Documentation can be found at readthedocs.