Theia Cloud is a fully browser-based Integrated Development Environment (IDE) that enables users to write, execute, and manage code without local installations. As Theia Cloud becomes increasingly integrated into educational platforms like Artemis, ensuring its reliability, usability, and scalability is crucial, particularly in large-scale environments with high concurrent usage. This thesis aims to investigate these challenges by developing a testing framework for Theia Cloud, focusing on End-to-End UI Testing to verify the correctness and stability of interactive features and Scalability and Load Testing by simulating realistic user interactions to evaluate Theia Cloud’s performance under high concurrent usage. The proposed approach will involve designing a maintainable Playwright test suite, developing a scalable test infrastructure, and analyzing system performance.