The emergence of digital-first assessments is prompting reconsideration of, and innovation in, aspects of psychometrics, test validation, and test use. Using the Duolingo English Test (DET) as an example, this three-paper series seeks to address issues concerning the estimation of classification consistency and the reporting of results for such assessments. The first paper presents a simulation study investigating the use of CTT-based classification consistency methods in a computer-adaptive testing context. The second paper further investigates CTT-based classification consistency estimates by applying the methods from the first paper, as well as a bootstrapping-inspired approach, to operational test data from the DET. The third paper investigates the reporting of test-related information and test-taker results to results users through a focus group with North American postsecondary admissions professionals. Collectively, the studies address challenges in constructing validity arguments for digital-first high-stakes assessments. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]