We argue (1) that the domains of externally mandated tests should be transparent to teachers, (2) that test maps can be used to communicate with teachers, and (3) that the most effective test maps express domains in terms of combinations of what students know and can do. We propose a device called a heuristic as the lowest level of specificity in a test map, and criteria to achieve a balance between too much specificity and too much generality in heuristics. Although we focus primarily on summative assessments, we also discuss how a state may use related, teacher-developed formative assessments to foster information-rich classroom environments. Other than item bank structure and sampling, our suggestions would have little impact on how tests are developed or scored, but we believe they would have a large impact on how they are described and used, and ultimately on their effectiveness as agents of instructional reform.