Auctions are important market mechanisms for the allocation of goods and services. Combinatorial auctions are those auctions in which buyers can place bids on combinations of items. Combinatorial auctions have many applications. The paper presents the CRAB software system. CRAB is a non-commercial software system for generating, solving, and testing of combinatorial auction problems. The system solves problems by the researcher method or by the primal-dual algorithm. CRAB is implemented in Ruby and it is distributed as the file crab.rb. The system is freely available on web pages for all interested users.