The pre-test – treatment – post-test design in experimental research has long been a hallmark of psychological and educational studies emulating natural science research practices. In Dynamic Assessment (DA), an analogue to this design emerged as a means of understanding learner responsiveness to mediation (Haywood, Lidz, Dynamic assessment in practice. Clinical and educational applications. Cambridge University Press, New York, 2007). DA derives from L. S. Vygotsky’s (The collected works of L. S. Vygotsky. Volume 1: problems of general psychology, including the volume thinking and speech (Rieber RW, Carton AS, eds). Plenum, New York, 1987) argument that psychological functions that are not yet fully developed but are still ripening may be made visible through joint functioning on the dialogic plane of interpsychological functioning. Specifically, the quality of dialogic support learners require while cooperating with a teacher, or mediator, along with their responsiveness to such support is interpreted as indicative of how near they are to more independent functioning. In DA, the use of a pre-test serves to establish a baseline of learner abilities prior to the introduction of mediation while post-tests allow for determining gains made by learners following mediation. Sternberg and Grigorenko (Dynamic testing. The nature and measurement of learning potential. Cambridge University Press, Cambridge, 2002) dubbed this the sandwich format of DA, and it has been the most widely used in cognitive education and psychology. In this chapter, we report the implementation of a sandwich DA project involving U.S. university learners of L2 French. The aim of the project was to help teachers mark student mastery of particular features of the language as they progress to the next level of study. In line with previous DA research (e.g., Davin and Donato 2013; Poehner et al, Lang Test 32(3):337–357, 2015), pre- and post-test comparisons were found to provide insights into learner abilities. However, additional conceptual work regarding manifestations of learner abilities during the procedure was required to more fully capture development. Following the work of Ollman (2003) on dialectics, which forms the driving logic behind Vygotsky’s theory, a reorientation to the sandwich format of DA is proposed. We argue that the entire procedure constitutes the assessment, a position that contrasts with the more conventional view of two distinct measures and an intervening treatment phase. Regarded as a unity, the procedure brings into focus not isolated snapshots of learner abilities at two points in time but rather a picture of the processes of learner development through time. This shift in view offered qualitatively different insights into learner abilities. In particular, learner initial performance, quality of interaction, receptivity to instruction, and subsequent changes to performance afforded a profiling of abilities in the process of development and documentation of instructional investment required to provoke change. Given the practical value of such information to teachers and learners, we advocate increased attention to the importance of time in assessment, not as a discrete occasion for glimpsing learner abilities but as unfolding across activities.