Automation testing is crucial in Agile development due to its ability to expedite testing processes, ensuring that rapid development cycles are supported by equally swift and reliable testing methods. Before Agile's rise, the Waterfall model was dominant, where testing occurred only after the development phase, often leading to time-consuming redevelopments and delayed releases. Agile, by contrast, emphasizes continuous integration, development, and deployment, requiring testing to keep pace with frequent updates and iterations. Automation testing addresses this need by using tools like Selenium and Appium to conduct repetitive, extensive tests efficiently, ensuring new features do not disrupt existing ones and that defects are detected early. It allows for consistent testing across various environments and conditions, thus improving reliability and performance. Despite the initial investment, automation testing offers high returns and efficiency, enabling Agile teams to overcome challenges like inadequate test coverage, broken code from frequent builds, and performance bottlenecks, ultimately enhancing speed, reliability, and code reusability in software development.