The paper identifies three central arguments against testing in the broader research literature. The first is a political argument, which argues that testing is a negative instrument of surveillance, and implies a diminishing trust in teacher professionalism. The second argument is a pedagogical one; it contends that testing negatively affects both the breadth and depth of pedagogy. The third argument is more conceptual ; it draws attention to the knowledge consequences of testing and how assessment can fragment knowledge into isolated facts. What has been neglected is a consideration of testing as a means for signalling appropriate knowledge, in terms of its coherence, sequence, progression and pace. The paper investigates the ways in which test results hold the potential to signal curriculum knowledge and therefore can drive pedagogical possibility rather than closure.