Software that works.
In production.

Run Your Coding Assistant in the IDE Terminal

For a long time I ran my coding assistant in a separate terminal window. Claude Code or Mistral Vibe on one side of the screen, IntelliJ on the other. It worked, but I had to switch windows to see what the assistant had done, and then find the files it had touched. More often than I like to admit, I didn't bother. I read the summary in the terminal and moved on.

Characterization Tests: A Safety Net Before You Refactor Legacy Code

You want to refactor a class and the tests you were counting on are not there. Or they are there, but they aim somewhere else and none of them would notice if you got this particular piece wrong. The code works, presumably, since it has been in production for years. You just have no way to prove that it still works once you have touched it.

Characterization tests are for this situation. You write tests that describe what the code does right now, and then you refactor with those tests watching your back.

Migrating from Spark to Javalin: You Can't Strangle a Web Framework

Changing a web framework must be done the same way you would change an aircraft engine midair. You do it prudently, in small, safe steps all the way. You test everything so no surprise surface when you do the switch.

I moved LogEze to Javalin. It is a product I have built since 2014, and it ran on the Spark Java web framework until recently. The cutover was one environment variable. I flipped it and everything switched from Spark to Javalin at once. Most of the work was in the preparations. Two weeks of them were hands-on work, abstracting Spark away from the core of the app far enough that a parallel Javalin implementation could be built alongside it and switched on safely. The rest started a lot earlier, with spikes to settle on the replacement and a shared super class that every controller already ran through, in place more than two years before I needed it.