https://pacolmg.com/en Pragmatic software architecture and maintainable systems. en Mon, 31 Aug 2026 00:00:00 GMT 1440 https://pacolmg.com/en/articles/dependency-direction A dependency between two pieces of code is never symmetric — one side breaks when the other changes. Pointing it at the right side is the entire discipline. Mon, 31 Aug 2026 00:00:00 GMT https://pacolmg.com/en/articles/dependency-direction architecture https://pacolmg.com/en/articles/case-file-migrating-a-legacy-reservation-handler A tangled legacy handler gets pulled apart one bounded step at a time, behind the safety net the earlier testing series already built. Mon, 24 Aug 2026 00:00:00 GMT https://pacolmg.com/en/articles/case-file-migrating-a-legacy-reservation-handler legacy refactoring https://pacolmg.com/en/articles/testing-a-legacy-project-with-an-ai-agent Most engineers already use AI to write code. Here's how to sequence an agent through testing a legacy codebase, without doing it all in one big step. Sat, 22 Aug 2026 00:00:00 GMT https://pacolmg.com/en/articles/testing-a-legacy-project-with-an-ai-agent testing legacy https://pacolmg.com/en/articles/testing-strategy-for-a-codebase-with-no-tests A codebase with no tests doesn't need unit tests for new features first. It needs an end-to-end net at the points where the business is most fragile. Sat, 08 Aug 2026 00:00:00 GMT https://pacolmg.com/en/articles/testing-strategy-for-a-codebase-with-no-tests testing legacy https://pacolmg.com/en/articles/first-test-in-a-file-with-none I didn't choose my first test — a production incident chose it for me. What that taught me about testing the highest-risk behavior first. Tue, 28 Jul 2026 00:00:00 GMT https://pacolmg.com/en/articles/first-test-in-a-file-with-none testing