Dynamic Assessment (DA) derives from Vygotsky's (1987) insight that the use of mediation, attuned to learner needs, enables learners to perform beyond their current level of functioning, thereby providing insights into emerging capabilities. The instructional quality of mediation means that this process simultaneously creates possibilities for development, even over the course of a single session, a phenomenon referred to as "microgenesis" (Wertsch, 1985). An important feature of DA is transfer, or transcendence: the process of tracking learner development as it unfolds not only with regard to control of tasks included in an assessment but also more complex and difficult tasks that build on those included in the original instrument (Campione, Brown, Ferrera, & Bryant, 1984; Feuerstein, Rand, & Hoffman, 1979; Poehner, 2007). The present study reports on the use of DA principles in tests of second language (L2) listening and reading comprehension delivered through an online format. The tests, which incorporate mediation, include transfer items to determine the extent to which learner development is supported during the test. This process generates three scores: actual (to capture unmediated performance); mediated (reflecting responsiveness to assistance provided on each test item); and a learning potential score (based on gain between actual and mediated performance) that indicates how much investment in future instructional activity is likely required for development to move forward. (Contains 4 tables, 3 figures, and 7 notes.)