Traditionally in formal testing during many language courses, students are required to take a vocabulary or grammar exam. Such exams, be they progress or proficiency ones, are usually conducted in paper format at the end of the given study period, or at set stages during the course.
Although such a procedure was and is widely accepted for the purposes of the course, the advent of electronic flashcards has presented language course stake-holders (students, teachers, or administrators) with various opportunities concerning informal vocab or grammar testing, and even course content. Such informal testing can be used to supplement and, in some cases, even replace formal testing.
The first opportunity is the chance for participants to test themselves on a daily basis with immediate feedback. This is, effectively, learning via testing, but with more readily available information as to performance and difficulty, with more and more extension features coming online.
The second advantage of this informal testing is the ability of students to choose the temp at which they tests themselves on different items. If they choose to do so, they can learn items via self-testing before even covering them formally in the course. The last feature is the chance to increase the range of testing content within the duration of the course, based on the progress that students are making.
Although scorer reliability may certainly be of concern, particularly for higher-stakes situations, this can be mitigated by the use of more traditional formal testing, where flashcards would serve more as a learning and general feedback tool.