Explore test-driven development (TDD) for APIs in this 41-minute EuroPython 2015 conference talk by Michael Kuehne. Learn how to validate complex API functionality, drive API design towards better usability, and implement TDD principles using Django. Discover practical approaches to API architecture, isolation, and output testing, along with strategies for handling unknown factors, unit tests, and acceptance tests. Dive into the BDD cycle, test numbering, and architecture, while gaining insights on setting up test environments, versioning endpoints, and managing asynchronous behaviors with Celery. Benefit from Kuehne's lessons learned in customer projects and understand how TDD can lead to inverse design improvements for APIs.