The assessment of second language (L2) pragmatic competence typically involves questionnaires, such as discourse completion tasks. This article describes a novel approach to using questionnaires to assess L2 metapragmatic capacities while simultaneously promoting their development: engaging learners in cooperative interaction as they complete the task. Following dynamic assessment principles, cooperative interaction reveals both fully formed and emerging competencies (i.e. zone of proximal development) while at the same time furthering their continued growth. This study draws on data collected during a concept-based pedagogical enrichment program in which US university students of French were learning the concepts of social distance and power hierarchies as illustrated by the second-person pronouns "tu" and "vous" "you". We present a case study of one learner, Nikki, to show how support provided by a tutor around one questionnaire item (i.e. choosing "tu" or "vous" in an ambiguous situation) both assessed and promoted her developing conceptual knowledge about the dynamics of interpersonal relationships and how these are indexed through language. (Contains 2 tables, 2 figures, and 4 notes.)