In professional writing, usability testing investigates how well users can find, understand, and use a document (Lannon). Usability testing involves gathering feedback from users, analyzing how successfully they used the document, and drawing on the test results to change or refine the design. From the authors' experiences as writers and teachers, they know the power of usability and user-centered design. Usability testing allows students to engage with a real audience. Not only do they envision this audience by writing a detailed persona, but they also meet them and engage in an iterative process with them, often learning about their misconceptions and stereotypes and gaining new insights about the audience. Usability testing also gives students direct and unvarnished feedback on their writing. Along the way, students move from thinking of their audience as a nebulous concept toward knowing readers as real people--and they understand more fully that writing is an act with real consequences.