End-to-end testing is a comprehensive software testing methodology that evaluates the functionality and behavior of an application from start to finish, simulating real-world user scenarios. It involves testing the entire application flow, including all integrated components, subsystems, and dependencies, to ensure that the software behaves as expected and meets the specified requirements.

In end-to-end testing, testers interact with the application as an end-user would, starting from the entry point and proceeding through all the steps until the desired outcome is achieved or the process is completed. This testing approach verifies that all components of the application work together seamlessly and that data is transferred correctly between them.

End-to-end testing aims to validate critical business processes, user workflows, and system integrations, identifying any issues or defects that may arise along the way. It helps ensure that the application meets functional requirements, performs reliably under various conditions, and delivers a satisfactory user experience.

Overall, end-to-end testing plays a crucial role in validating the entire software application, from the user interface to the backend systems, ensuring its quality, reliability, and performance before deployment.