We test frontends across multiple environments using a combination of local network (LAN) testing, simulators and physical devices. During development, the application is served over the local network so it can be accessed simultaneously on real devices such as Android phones, iPhones, tablets, laptops and monitors of varying screen sizes. We also use device simulators and browser tools to test responsiveness, layout behavior and edge cases across different resolutions and browsers. This mix of real-device and simulated testing helps ensure the frontend behaves consistently across platforms before release.