Evaluation and refinement of computational artifacts involves measuring, testing, debugging, and responding to the changing needs and expectations of users. Aspects that can be evaluated include correctness, performance, reliability, usability, and accessibility. For example, after witnessing common errors with user input in a computational artifact, students could refine the artifact to validate user input and provide an error message if invalid data is provided. Alternatively, students could observe a robot in a variety of lighting conditions to determine whether the code controlling a light sensor should be modified to make it less sensitive. Additionally, students could also incorporate feedback from a variety of end users to help guide the size and placement of menus and buttons in a user interface.