We introduce an educational game-based assessment that measures the choices students make while learning. We present Posterlet, a game designed to assess students' choices to seek negative feedback and to revise, in which students learn graphical design principles while creating posters. We validate our game-based assessment approach with three research studies, in which college and middle-school students play Posterlet and then complete a posttest. Results showed that the game helped students learn: students who played Posterlet before completing the posttest learned more graphical design principles than students who only completed the posttest. Moreover, the choices to seek negative feedback and to revise can predict learning and be used as valid outcome measures for learning. We present a first-of-kind examination of students' choices to seek feedback and to revise, as well as of students' learning outcomes based on these choices, which can be used to develop and evaluate models of instruction that help students make informed learning choices. [For the complete proceedings, see ED557311.]