Containerized end-to-end testing provides advantages like isolation of environments, reproducible application environments, and optimized parallel execution. Sakuli is an open source tool that allows defining end-to-end tests using JavaScript or Java and executing them within Docker containers. It supports testing graphical user interfaces using technologies like X11 forwarding or VNC. Sakuli provides functions for web testing and interacting with applications and defines a structure for test cases with initialization, test steps, and exception handling. It can integrate with monitoring and CI tools to report test results.