Explore the world of testing doubles in Python through this 25-minute EuroPython Conference talk. Dive deep into mocks, fakes, dummies, stubs, and spies, understanding their differences and appropriate use cases. Learn how to effectively isolate dependencies in your tests using unittest.mock, including new features in Python 3.7. Gain insights from the writings of Gerard Meszaros and Martin Fowler, and discover advanced techniques to shape mock objects for different functional behaviors. Suitable for both beginners and intermediate developers, this talk covers the importance of doubles, main qualities of a double, an overview of unittest.mock, and detailed explanations of various testing doubles. Conclude with practical takeaways and a Q&A session to enhance your Python testing skills.