Conf42: Python 2022


How to TDD in legacy code

Gil Zilberfeld
Wizard of Testing @ TestinGil

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“TDD is great, but it won’t work on our legacy code”. I hear that a lot. That’s why people don’t even give TDD a try. Their code is killing their hope.

TDD’s basic examples are, well, basic, and have no relationship to real-world code. But it can work on legacy code, and everyone’s got that. You just need to remember a few techniques, stick to the principles, and you can start doing TDD in your application code tomorrow.

In this session I’ll show how to do it, the techniques and principles involved. And I’ll show how to add TDD code inside an ugly application.

No more excuses then. It’s possible to do TDD right there in your own legacy code. Let’s do it. Key points - TDD may not seem applicable in “real code”, but the principles apply - Use characterization tests as a safety net - Use test-first principles to add new features and fix bugs - Refactor before and after adding code

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