Component-based usability testing is when you test the different pieces or parts (called components) to see how easy and useful they are to use. To do this, you first make sure you have a list of all the components that make up your product. Then you find people to try to use the components and give you feedback on how easy or difficult it was to use them. This feedback can help you figure out what needs to be changed or improved to make it easier for people to use your product.