Supply Chain Formation (SCF) is the process of determining the participants in a supply chain, who will exchange what with whom, and the terms of the exchanges. Mixed multi-unit combinatorial auctions (MMUCAs) offer a high potential to solve SCF problems, and thus be employed for the automated assembly of supply chains of agents. In this paper we present MMUCATS, a test suite for MMUCAs that allows researchers to test, compare, and improve their winner determination algorithms for MMUCAs. Categories and Subject Descriptors F.2 [Analysis of Algorithms and Problem Complexity]: Nonnumerical Algorithms and Problems General Terms Algorithms, Experimentation, Economics Keywords Combinatorial Auctions, Supply Chain Management