Although it is often recognised that testing has unintended effects, not enough intellectual curiosity has been invested in a deeper questioning of what "unintended" means. While this concept often remains dependent on an image of good, underlying, rational intentions, it underestimates the contested, controversial and socially productive nature of testing. A conceptual alternative is offered, termed "constitutive effects" as well as a theoretical framework in which this concept makes sense. Four domains in which constitutive effects are likely to unfold are carved out. A qualitative case study of how a national testing system of Danish for immigrants influences practices in one school in Denmark is offered as an illustration of such constitutive effects. Finally, a discussion unfolds concerning in what sense constitutive effects of testing can be seen as political (in a way that is not captured by the more conventional conceptualisation of "unintended effects".