After we’ve addressed all the deprecation warnings and successfully dual-booted an application, the next step in a Rails upgrade is often the most challenging: fixing the broken build.
At this point, the test suite is red, and our job is to bring it back to green. This phase can feel chaotic, but over the years at FastRuby.io, we’ve developed a process that makes it systematic and (relatively) predictable.
In this post, I’ll break down how we approach this step, what patterns we’ve noticed, and how we debug the trickiest failures.
Our “Fix Broken Build” Process
Attack errors before failures
When a test suite runs, errors (exceptions, missing methods, or crashes) block progress. They…









![[8/4] How a Scotsman saved hours of my time by turning an LLM into my virtual assistant](https://digitalpress.fra1.cdn.digitaloceanspaces.com/xhtzjbw/2025/12/ChatGPT-Image-Dec-27--2025--05_51_01-AM.png)
![[8/4] How a Scotsman saved hours of my time by turning an LLM into my virtual assistant](https://digitalpress.fra1.cdn.digitaloceanspaces.com/xhtzjbw/2025/10/Screenshot-2025-10-26-at-10.25.22.png)
![[8/4] How a Scotsman saved hours of my time by turning an LLM into my virtual assistant](https://digitalpress.fra1.cdn.digitaloceanspaces.com/xhtzjbw/2025/10/Screenshot-2025-10-26-at-10.26.09.png)





![[7/4] Speak to LLMs with voice-to-text](https://digitalpress.fra1.cdn.digitaloceanspaces.com/xhtzjbw/2025/12/christmas-llm-post-7-4-1.png)
