Explore dependency isolation techniques and their impact on API design in this 25-minute EuroPython 2020 conference talk. Discover how testing frameworks can influence system architecture and learn practical strategies for creating clean, readable tests. Dive into unittest.mock library and pytest framework basics, examining their potential through real-world scenarios. Gain insights on structuring code for improved testability, ensuring clarity, and maintaining a robust Continuous Integration platform. Suitable for beginner Pythonistas seeking clean code structuring and testing methods, as well as intermediate developers looking to refresh their knowledge on dependency isolation with practical examples.