78: Lean TDD with Brian Okken

Brian Okken, lead engineer at Rohde & Schwarz, creator of the pytest book and course, and author of the new book Lean TDD, joins us to rethink test driven development. His core argument: write tests at the highest level that still makes sense, so you can refactor, restructure, and hand work to an agent without rewriting your suite every time. We dig into why function-level tests with heavy mocking are often harder to write than system-level tests, why the "TDD takes too long" complaint usually comes from testing at the wrong level, and why old rules about test speed no longer hold up on modern machines and CI.

The conversation also covers the lean side of Lean TDD: what counts as waste in a test suite, when to delete tests you wrote on the way to a better one, and why a thousand tests is not automatically better than twenty. Brian shares how caring about the whole system rather than just his slice of it changed his career, how he works with AI agents while still reading every line they produce, the stigma around test engineering roles, and what he learned self-publishing a 100 page book and recording the audiobook himself. He closes with advice for newer engineers on large codebases and why everyone is winging it more than you think.

• Lean TDD Book: https://leantdd.com/

• Free sample chapter (chapter 1): https://leantdd.com/downloads/lean-tdd-chapter-1-sample.pdf

• Brian’s Blog: https://pythontest.com/

• Brian’s LinkedIn: https://www.linkedin.com/in/okken/

• Brian on GitHub: https://github.com/okken

• pytest course: https://pythontest.com/courses

• Test & Code podcast: https://testandcode.com

Hosts

• Overcommitted: https://overcommitted.dev
• Brittany Ellich: https://brittanyellich.com
• Erika Eggemeyer: https://github.com/eggyhead