How to Parallelize Your RSpec Test Suite Locally - FastRuby.io | Rails Upgrade Service

Waiting over an hour for a test suite to finish is a productivity killer. On a recent project, that was our reality. Running the full local RSpec suite took almost 2 hours, making it difficult to get quick feedback and confidently iterate on changes. While there are many ways to optimize test performance opens a new window including fixtures, request stubbing, faster tooling, and more, most of these options require significant effort to implement. Instead, we explored a simpler approach: bringing parallel test execution to local development. The result was a much faster feedback loop (down to 5 minutes) and a significantly better developer experience. Although our primary goal was to improve the local developer experience, this setup can be used in both local and CI environments. In this post, we’ll walk through how to set up parallel testing locally in Rails, from configuring worker-specific databases to preparing your application for concurrent test execution.