With hundreds of on-chip memories to test, it can be desirable to share some of the testing architecture among memories. We present a software, the Memory Bist Optimizer (MBO) that automatically computes an optimized sharing of BIST blocks among the memories of a SOC. It accepts arbitrary sharing rules, and can handle dedicated, parallel, and sequential wrappers. Area, testing power and testing time are considered simultaneously. MBO is completely technology-node-independant.