This tutorial provides a comprehensive guide on integrating test coverage tracking into a Ruby codebase using CircleCI and Coveralls. It begins by creating a sample Ruby project with test coverage, setting up a CI pipeline, and sending coverage results to Coveralls, a free service for open-source projects. The tutorial emphasizes the importance of test coverage as a measure of codebase health, detailing how Simplecov, a Ruby coverage tool, can be configured to generate reports. It explains the use of CircleCI's orb technology to facilitate integration with Coveralls, detailing the configuration file setup and execution of RSpec tests within a Docker environment containing Ruby and Node. The tutorial outlines how to convert coverage reports to the LCOV format required by Coveralls using the simplecov-lcov gem and guides through the process of uploading these reports securely via a COVERALLS_REPO_TOKEN. Finally, it discusses the benefits of automated test coverage updates, including badging, PR comments, and pass/fail checks, while encouraging further exploration of more complex scenarios and leveraging parallelism for larger projects.