What are the three main approaches to usability testing? ⬇️ Low-fidelity testing: involves paper prototyping at the concept stage to get early feedback on the design. ↕️ Mixed-fidelity testing: involves a clickable prototype that simulates the app's functionality and allows users to interact with the visual side of the app. ⬆️ High-fidelity testing: involves a fully functioning prototype with full clickability and sometimes actual code. This type of testing is done when the app is on test flight