We often think production bugs happen because of big oversights or complex logic failures. But sometimes, it’s the smallest things—a single typo—that sneak past every safeguard and cause trouble in live environments. Recently, I had one such experience in a Rails project. It wasn’t a major crash, but it did break a piece of business logic under specific conditions. More importantly, it taught me valuable lessons about code reviews, rubocop, and testing discipline—lessons I’d like to share here. The Safeguards We Already Had Like most teams, we don’t push code directly to production. Instead, we follow a layered safety net: ✅ Pre-commit checks to catch obvious mistakes ✅ RSpec test cases to validate logic ✅ CI pipelines to enforce standards and run checks ✅ Code reviews to ensure human oversight ✅ QA testing before deployment You’d think with all this in place, no typo could possibly slip through. So how did it happen? Where Things Went Wrong: Rubocop and a “Helpfu...
We often think production bugs happen because of big oversights or complex logic failures. But sometimes, it’s the smallest things—a single typo—that sneak past every safeguard and cause trouble in live environments.
Recently, I had one such experience in a Rails project. It wasn’t a major crash, but it did break a piece of business logic under specific conditions. More importantly, it taught me valuable lessons about code reviews, rubocop, and testing discipline—lessons I’d like to share here.
The Safeguards We Already Had
Like most teams, we don’t push code directly to production. Instead, we follow a layered safety net:
-
✅ Pre-commit checks to catch obvious mistakes
-
✅ RSpec test cases to validate logic
-
✅ CI pipelines to enforce standards and run checks
-
✅ Code reviews to ensure human oversight
-
✅ QA testing before deployment
You’d think with all this in place, no typo could possibly slip through. So how did it happen?
Where Things Went Wrong: Rubocop and a “Helpful” Auto-Fix
In this Rails project, we rely on Rubocop for code style enforcement. Normally, we fix issues in one of two ways:
-
Manually correcting the code
-
Running rubocop -A for automatic fixes
But this time, I chose a third option: letting my AI-powered IDE auto-suggest fixes. And that’s where the trouble began.
The IDE suggested changing this:
.order("start_date DESC") # Existing
#to this:
.order(start_date: :des) # Auto-suggested
Notice the problem? :des is a typo—it should have been :desc.
Rubocop didn’t catch it. Tests didn’t cover that exact line. Reviewers missed it. And before we knew it, the code went live.
The Aftermath
A few hours after deployment, we noticed the issue in a read-replica query. By then, the rake task had already run. Thankfully, the impact was limited, and we quickly reverted the change.
After proper testing, we fixed the issue and redeployed safely. But the lesson was loud and clear: automation is powerful, but not infallible.
Key Takeaways for Rails Developers
Here are the practical lessons I walked away with:
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Don’t skip QA when unrelated code changes occur. Even if you’re only fixing style or small tweaks, ensure major areas affected by the change get tested.
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Review staged changes before committing. Don’t blindly trust auto-fixes. Double-check what’s being committed in your name.
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Re-review your PR on GitHub or GitLab. Even after staging, a second look often catches mistakes that slip through the first pass.
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Stay aware of “helpful” AI and IDE suggestions. They’re great tools—but you own the final responsibility for what’s shipped.
Final Thoughts
This experience reinforced something every Rails developer should remember: typos are small, but their impact isn’t. Between Rubocop, CI pipelines, and human reviews, we have strong safety nets—but no safeguard replaces mindful coding and thorough reviews.
So the next time your IDE “helpfully” suggests a change, pause for a second. That quick check might save you from the kind of bug that inspired this post.
👉 What about you? Have you ever had a tiny mistake sneak into production despite all your safeguards? I’d love to hear your stories in the comments.
from
https://dev.to/madhuhari188/the-one-letter-rails-bug-that-slipped-past-rubocop-ci-and-code-reviews-12im
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