The main focus in the community of test developers and researchers is on improving adaptive test procedures and methodologies. Yet, the transition from research projects to larger-scale operational CATs is facing its own challenges. Usually, these operational CATs find their origin in government tenders. “Scalability”, “Interoperability” and “Transparency” are three keywords often found in these documents. Scalability is concerned with parallel system architectures which are based upon stateless selection algorithms. Design capacities often range from 10,000 to well over 100,000 concurrent students. Interoperability is implemented in standards like QTI, standards that were not designed with adaptive testing in mind. Transparency is being realized by open source software: the adaptive test should not be a black box. These three requirements often complicate the development of an adaptive test, or sometimes even conflict.

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