Abstract. Recent advancements in the assessment of Complex Problem Solving (CPS) build on the use of homogeneous tasks that enable the reliable estimation of CPS skills. The range of problems featured in established instruments such as MicroDYN is consequently limited to a specific subset of homogeneous complex problems. This restriction is problematic when looking at domain-specific examples of complex problems, which feature characteristics absent from current assessment instruments (e.g., threshold states). We propose to utilize the formal framework of Finite State Automata (FSA) to extend the range of problems included in CPS assessment. An approach based on FSA, called MicroFIN, is presented, translated into specific tasks, and empirically investigated. We conducted an empirical study (N = 576), (1) inspecting the psychometric features of MicroFIN, (2) relating it to MicroDYN, and (3) investigating the relations to a measure of reasoning (i.e., CogAT). MicroFIN (1) exhibited adequate measurement characteristics and multitrait-multimethod models indicated (2) the convergence of latent dimensions measured with MicroDYN. Relations to reasoning (3) were moderate and comparable to the ones previously found for MicroDYN. Empirical results and corresponding explanations are discussed. More importantly, MicroFIN highlights the feasibility of expanding CPS assessment to a larger spectrum of complex problems.