Verify your assumptions

That’s what I keep preaching to my team but still fail at myself every so often.

This week, I wasted a whole day implementing a fix for a bug that wasn’t there. My task was to add one line to a configuration file in a Chef cookbook. When I ran its test suite, it surprisingly failed and it was clear that my simple change couldn’t be the cause. I assumed it was due to recent changes in software packages installed by the cookbook. So I started adapting our old code to these changes, and one change led to another, and another, until I finally realised that over the course of multiple hours, my one-line bugfix had turned into a full code overhaul. How did I get here?

I decided to start from scratch. git reset --hard HEAD. I quickly fixed my config file and ran the tests. When they failed again, closer inspection revealed that it was actually just the same test failing twice. The cause was a bug that had found its way into the main branch without breaking the CI pipeline (finding the reason for this will be interesting). It had been there all along! After another one-line fix, my change was ready for review. Round 2 had taken me less than half an hour.

The lesson: Don’t rush into battle blindly. Look closely. Identify assumptions and verify them. It might just be windmills!

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