After 25 years with TDD, we are now parting ways. The incremental TDD steps were great for human cognition, but didn't survive the transition to agentic coding.

Test-Driven Development (TDD) has been my default programming mode for 25 years. TDD simply made me a better developer. It’s been invaluable.

However, the time has come to bid farewell to my old companion. Agentic coding is sufficiently different from manual coding, meaning we need to question existing development principles and practices. And TDD didn’t survive my transition into AI-native development: forcing an agent through increments optimized for human cognition negates many of the benefits.

This article reflects on my decades as a TDD practitioner as well as the agentic characteristics that made me abandon the technique. As customary, we’ll start from the beginning.